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CGI(3)                 Perl Programmers Reference Guide                 CGI(3)



NAME
       CGI - Simple Common Gateway Interface Class

SYNOPSIS
         # CGI script that creates a fill-out form
         # and echoes back its values.

         use CGI qw/:standard/;
         print header,
               start_html('A Simple Example'),
               h1('A Simple Example'),
               start_form,
               "What's your name? ",textfield('name'),p,
               "What's the combination?", p,
               checkbox_group(-name=>'words',
                              -values=>['eenie','meenie','minie','moe'],
                              -defaults=>['eenie','minie']), p,
               "What's your favorite color? ",
               popup_menu(-name=>'color',
                          -values=>['red','green','blue','chartreuse']),p,
               submit,
               end_form,
               hr;

          if(3,n) (param()) {
              print "Your name is",em(param('name')),p,
                    "The keywords are: ",em(join(1,n)(", ",param('words'))),p,
                    "Your favorite color is ",em(param('color')),
                    hr;
          }

ABSTRACT
       This perl library uses perl5 objects to make it easy to create Web
       fill-out forms and parse their contents.  This package defines CGI
       objects, entities that contain the values of the current query string(3,n)
       and other state variables.  Using a CGI object's methods, you can exam-
       ine keywords and parameters passed to your script, and create forms
       whose initial values are taken from the current query (thereby preserv-
       ing state information).  The module provides shortcut functions that
       produce boilerplate HTML, reducing typing and coding errors. It also
       provides functionality for some of the more advanced features of CGI
       scripting, including support for file(1,n) uploads, cookies, cascading style
       sheets, server push, and frames.

       CGI.pm also provides a simple function-oriented programming style for
       those who don't need its object-oriented features.

       The current version(1,3,5) of CGI.pm is available at

         http://www.genome.wi.mit.edu/ftp/pub/software/WWW/cgi_docs.html
         ftp://ftp-genome.wi.mit.edu/pub/software/WWW/

DESCRIPTION
       PROGRAMMING STYLE

       There are two styles of programming with CGI.pm, an object-oriented
       style and a function-oriented style.  In the object-oriented style you
       create one or more CGI objects and then use object methods to create
       the various elements of the page.  Each CGI object starts out with the
       list of named(5,8) parameters that were passed to your CGI script by the
       server.  You can modify the objects, save them to a file(1,n) or database
       and recreate them.  Because each object corresponds to the "state" of
       the CGI script, and because each object's parameter list is independent
       of the others, this allows you to save the state of the script and
       restore it later.

       For example, using the object oriented style, here is how you create a
       simple "Hello World" HTML page:

          #!/usr/local/bin/perl -w
          use CGI;                             # load(7,n) CGI routines
          $q = new CGI;                        # create new CGI object
          print $q->header,                    # create the HTTP header
                $q->start_html('hello world'), # start the HTML
                $q->h1('hello world'),         # level 1 header
                $q->end_html;                  # end the HTML

       In the function-oriented style, there is one default CGI object that
       you rarely deal with directly.  Instead you just call functions to
       retrieve CGI parameters, create HTML tags, manage cookies, and so on.
       This provides you with a cleaner programming interface, but limits you
       to using one CGI object at a time.  The following example prints the
       same page, but uses the function-oriented interface.  The main differ-
       ences are that we now need to import a set(7,n,1 builtins) of functions into our name
       space (usually the "standard" functions), and we don't need to create
       the CGI object.

          #!/usr/local/bin/perl
          use CGI qw/:standard/;           # load(7,n) standard CGI routines
          print header,                    # create the HTTP header
                start_html('hello world'), # start the HTML
                h1('hello world'),         # level 1 header
                end_html;                  # end the HTML

       The examples in(1,8) this document mainly use the object-oriented style.
       See HOW TO IMPORT FUNCTIONS for important information on function-ori-
       ented programming in(1,8) CGI.pm

       CALLING CGI.PM ROUTINES

       Most CGI.pm routines accept(2,8) several arguments, sometimes as many as 20
       optional ones!  To simplify this interface, all routines use a named(5,8)
       argument calling style that looks like this:

          print $q->header(-type=>'image/gif',-expires=>'+3d');

       Each argument name is preceded by a dash.  Neither case nor order mat-
       ters in(1,8) the argument list.  -type, -Type, and -TYPE are all acceptable.
       In fact, only the first argument needs to begin with a dash.  If a dash
       is present in(1,8) the first argument, CGI.pm assumes dashes for the subse-
       quent ones.

       Several routines are commonly called with just one argument.  In the
       case of these routines you can provide the single argument without an
       argument name.  header() happens to be one of these routines.  In this
       case, the single argument is the document type.

          print $q->header('text/html');

       Other such routines are documented below.

       Sometimes named(5,8) arguments expect a scalar, sometimes a reference to an
       array, and sometimes a reference to a hash.  Often, you can pass any
       type of argument and the routine will do whatever is most appropriate.
       For example, the param() routine is used to set(7,n,1 builtins) a CGI parameter to a
       single or a multi-valued value.  The two cases are shown below:

          $q->param(-name=>'veggie',-value=>'tomato');
          $q->param(-name=>'veggie',-value=>['tomato','tomahto','potato','potahto']);

       A large number of routines in(1,8) CGI.pm actually aren't specifically
       defined in(1,8) the module, but are generated automatically as needed.
       These are the "HTML shortcuts," routines that generate HTML tags for
       use in(1,8) dynamically-generated pages.  HTML tags have both attributes
       (the attribute="value" pairs within the tag itself) and contents (the
       part between the opening and closing pairs.)  To distinguish between
       attributes and contents, CGI.pm uses the convention of passing HTML
       attributes as a hash reference as the first argument, and the contents,
       if(3,n) any, as any subsequent arguments.  It works out like this:

          Code                           Generated HTML
          ----                           --------------
          h1()                           <h1>
          h1('some','contents');         <h1>some contents</h1>
          h1({-align=>left});            <h1 align="LEFT">
          h1({-align=>left},'contents'); <h1 align="LEFT">contents</h1>

       HTML tags are described in(1,8) more detail later.

       Many newcomers to CGI.pm are puzzled by the difference between the
       calling conventions for the HTML shortcuts, which require curly braces
       around the HTML tag attributes, and the calling conventions for other
       routines, which manage to generate attributes without the curly brack-
       ets.  Don't be confused.  As a convenience the curly braces are
       optional in(1,8) all but the HTML shortcuts.  If you like, you can use curly
       braces when calling any routine that takes named(5,8) arguments.  For exam-
       ple:

          print $q->header( {-type=>'image/gif',-expires=>'+3d'} );

       If you use the -w switch(1,n), you will be warned that some CGI.pm argument
       names conflict with built-in Perl functions.  The most frequent of
       these is the -values argument, used to create multi-valued menus, radio
       button clusters and the like.  To get around this warning, you have
       several choices:

       1.  Use another name for the argument, if(3,n) one is available.  For exam-
           ple, -value is an alias for -values.

       2.  Change the capitalization, e.g. -Values

       3.  Put quotes around the argument name, e.g. '-values'

       Many routines will do something useful with a named(5,8) argument that it
       doesn't recognize.  For example, you can produce non-standard HTTP
       header fields by providing them as named(5,8) arguments:

         print $q->header(-type  =>  'text/html',
                          -cost  =>  'Three smackers',
                          -annoyance_level => 'high',
                          -complaints_to   => 'bit bucket');

       This will produce the following nonstandard HTTP header:

          HTTP/1.0 200 OK
          Cost: Three smackers
          Annoyance-level: high
          Complaints-to: bit bucket
          Content-type: text/html

       Notice the way that underscores are translated automatically into
       hyphens.  HTML-generating routines perform a different type of transla-
       tion.

       This feature allows you to keep up with the rapidly changing HTTP and
       HTML "standards".

       CREATING A NEW QUERY OBJECT (OBJECT-ORIENTED STYLE):

            $query = new CGI;

       This will parse the input (from both POST and GET methods) and store it
       into a perl5 object called $query.

       CREATING A NEW QUERY OBJECT FROM AN INPUT FILE

            $query = new CGI(INPUTFILE);

       If you provide a file(1,n) handle to the new() method, it will read(2,n,1 builtins) parame-
       ters from the file(1,n) (or STDIN, or whatever).  The file(1,n) can be in(1,8) any of
       the forms describing below under debugging (i.e. a series of newline
       delimited TAG=VALUE pairs will work).  Conveniently, this type of file(1,n)
       is created by the save() method (see below).  Multiple records can be
       saved and restored.

       Perl purists will be pleased to know that this syntax accepts refer-
       ences to file(1,n) handles, or even references to filehandle globs, which is
       the "official" way to pass a filehandle:

           $query = new CGI(\*STDIN);

       You can also initialize the CGI object with a FileHandle or IO::File
       object.

       If you are using the function-oriented interface and want to initialize
       CGI state from a file(1,n) handle, the way to do this is with restore_param-
       eters().  This will (re)initialize the default CGI object from the
       indicated file(1,n) handle.

           open(2,3,n) (IN,"test.in") || die;
           restore_parameters(IN);
           close(2,7,n) IN;

       You can also initialize the query object from an associative array ref-
       erence:

           $query = new CGI( {'dinosaur'=>'barney',
                              'song'=>'I love you',
                              'friends'=>[qw/Jessica George Nancy/]}
                           );

       or from a properly formatted, URL-escaped query string:

           $query = new CGI('dinosaur=barney&color=purple');

       or from a previously existing CGI object (currently this clones the
       parameter list, but none of the other object-specific fields, such as
       autoescaping):

           $old_query = new CGI;
           $new_query = new CGI($old_query);

       To create an empty query, initialize it from an empty string(3,n) or hash:

          $empty_query = new CGI("");

              -or-

          $empty_query = new CGI({});

       FETCHING A LIST OF KEYWORDS FROM THE QUERY:

            @keywords = $query->keywords

       If the script was invoked as the result of an <ISINDEX> search, the
       parsed keywords can be obtained as an array using the keywords()
       method.

       FETCHING THE NAMES OF ALL THE PARAMETERS PASSED TO YOUR SCRIPT:

            @names = $query->param

       If the script was invoked with a parameter list (e.g.
       "name1=value1&name2=value2&name3=value3"), the param() method will
       return the parameter names as a list.  If the script was invoked as an
       <ISINDEX> script and contains a string(3,n) without ampersands (e.g.
       "value1+value2+value3") , there will be a single parameter named(5,8) "key-
       words" containing the "+"-delimited keywords.

       NOTE: As of version(1,3,5) 1.5, the array of parameter names returned will be
       in(1,8) the same order as they were submitted by the browser.  Usually this
       order is the same as the order in(1,8) which the parameters are defined in(1,8)
       the form (however, this isn't part of the spec, and so isn't guaran-
       teed).

       FETCHING THE VALUE OR VALUES OF A SINGLE NAMED PARAMETER:

           @values = $query->param('foo');

                     -or-

           $value = $query->param('foo');

       Pass the param() method a single argument to fetch the value of the
       named(5,8) parameter. If the parameter is multivalued (e.g. from multiple
       selections in(1,8) a scrolling list), you can ask to receive an array.  Oth-
       erwise the method will return a single value.

       If a value is not given in(1,8) the query string(3,n), as in(1,8) the queries
       "name1=&name2=" or "name1&name2", it will be returned as an empty
       string.  This feature is new in(1,8) 2.63.

       If the parameter does not exist at all, then param() will return undef
       in(1,8) a scalar context, and the empty list in(1,8) a list context.

       SETTING THE VALUE(S) OF A NAMED PARAMETER:

           $query->param('foo','an','array','of','values');

       This sets the value for the named(5,8) parameter 'foo' to an array of val-
       ues.  This is one way to change the value of a field AFTER the script
       has been invoked once before.  (Another way is with the -override
       parameter accepted by all methods that generate form elements.)

       param() also recognizes a named(5,8) parameter style of calling described in(1,8)
       more detail later:

           $query->param(-name=>'foo',-values=>['an','array','of','values']);

                                     -or-

           $query->param(-name=>'foo',-value=>'the value');

       APPENDING ADDITIONAL VALUES TO A NAMED PARAMETER:

          $query->append(-name=>'foo',-values=>['yet','more','values']);

       This adds a value or list of values to the named(5,8) parameter.  The values
       are appended to the end of the parameter if(3,n) it already exists.  Other-
       wise the parameter is created.  Note that this method only recognizes
       the named(5,8) argument calling syntax.

       IMPORTING ALL PARAMETERS INTO A NAMESPACE:

          $query->import_names('R');

       This creates a series of variables in(1,8) the 'R' namespace.  For example,
       $R::foo, @R:foo.  For keyword lists, a variable @R::keywords will
       appear.  If no namespace is given, this method will assume 'Q'.  WARN-
       ING:  don't import anything into 'main'; this is a major security
       risk!!!!

       NOTE 1: Variable names are transformed as necessary into legal Perl
       variable names.  All non-legal characters are transformed into under-
       scores.  If you need to keep the original names, you should use the
       param() method instead to access(2,5) CGI variables by name.

       NOTE 2: In older versions, this method was called import().  As of ver-
       sion(1,3,5) 2.20, this name has been removed completely to avoid conflict with
       the built-in Perl module import operator.

       DELETING A PARAMETER COMPLETELY:

           $query->delete('foo','bar','baz');

       This completely clears a list of parameters.  It sometimes useful for
       resetting parameters that you don't want passed down between script
       invocations.

       If you are using the function call interface, use "Delete()" instead to
       avoid conflicts with Perl's built-in delete operator.

       DELETING ALL PARAMETERS:

          $query->delete_all();

       This clears the CGI object completely.  It might be useful to ensure
       that all the defaults are taken when you create a fill-out form.

       Use Delete_all() instead if(3,n) you are using the function call interface.

       DIRECT ACCESS TO THE PARAMETER LIST:

          $q->param_fetch('address')->[1] = '1313 Mockingbird Lane';
          unshift @{$q->param_fetch(-name=>'address')},'George Munster';

       If you need access(2,5) to the parameter list in(1,8) a way that isn't covered by
       the methods above, you can obtain a direct reference to it by calling
       the param_fetch() method with the name of the .  This will return an
       array reference to the named(5,8) parameters, which you then can manipulate
       in(1,8) any way you like.

       You can also use a named(5,8) argument style using the -name argument.

       FETCHING THE PARAMETER LIST AS A HASH:

           $params = $q->Vars;
           print $params->{'address'};
           @foo = split(1,n)("\0",$params->{'foo'});
           %params = $q->Vars;

           use CGI ':cgi-lib';
           $params = Vars;

       Many people want to fetch the entire parameter list as a hash in(1,8) which
       the keys are the names of the CGI parameters, and the values are the
       parameters' values.  The Vars() method does this.  Called in(1,8) a scalar
       context, it returns the parameter list as a tied hash reference.
       Changing a key changes the value of the parameter in(1,8) the underlying CGI
       parameter list.  Called in(1,8) a list context, it returns the parameter
       list as an ordinary hash.  This allows you to read(2,n,1 builtins) the contents of the
       parameter list, but not to change it.

       When using this, the thing you must watch out for are multivalued CGI
       parameters.  Because a hash cannot distinguish between scalar and list
       context, multivalued parameters will be returned as a packed string(3,n),
       separated by the "\0" (null) character.  You must split(1,n) this packed
       string(3,n) in(1,8) order to get at the individual values.  This is the conven-
       tion introduced long ago by Steve Brenner in(1,8) his cgi-lib.pl module for
       Perl version(1,3,5) 4.

       If you wish to use Vars() as a function, import the :cgi-lib set(7,n,1 builtins) of
       function calls (also see the section on CGI-LIB compatibility).

       SAVING THE STATE OF THE SCRIPT TO A FILE:

           $query->save(FILEHANDLE)

       This will write(1,2) the current state of the form to the provided filehan-
       dle.  You can read(2,n,1 builtins) it back in(1,8) by providing a filehandle to the new()
       method.  Note that the filehandle can be a file(1,n), a pipe(2,8), or whatever!

       The format of the saved file(1,n) is:

               NAME1=VALUE1
               NAME1=VALUE1'
               NAME2=VALUE2
               NAME3=VALUE3
               =

       Both name and value are URL escaped.  Multi-valued CGI parameters are
       represented as repeated names.  A session record is delimited by a sin-
       gle = symbol.  You can write(1,2) out multiple records and read(2,n,1 builtins) them back in(1,8)
       with several calls to new.  You can do this across several sessions by
       opening the file(1,n) in(1,8) append mode, allowing you to create primitive guest
       books, or to keep a history(1,3,n,1 builtins) of users(1,5)' queries.  Here's a short example
       of creating multiple session records:

          use CGI;

          open(2,3,n) (OUT,">>test.out") || die;
          $records = 5;
          foreach (0..$records) {
              my $q = new CGI;
              $q->param(-name=>'counter',-value=>$_);
              $q->save(OUT);
          }
          close(2,7,n) OUT;

          # reopen for reading
          open(2,3,n) (IN,"test.out") || die;
          while (!eof(IN)) {
              my $q = new CGI(IN);
              print $q->param('counter'),"\n";
          }

       The file(1,n) format used for save/restore is identical to that used by the
       Whitehead Genome Center's data exchange format "Boulderio", and can be
       manipulated and even databased using Boulderio utilities.  See

         http://stein.cshl.org/boulder/

       for further details.

       If you wish to use this method from the function-oriented (non-OO)
       interface, the exported name for this method is save_parameters().

       RETRIEVING CGI ERRORS

       Errors can occur while processing user input, particularly when pro-
       cessing uploaded files.  When these errors occur, CGI will stop pro-
       cessing and return an empty parameter list.  You can test for the exis-
       tence and nature of errors using the cgi_error() function.  The error(8,n)
       messages are formatted as HTTP status codes. You can either incorporate
       the error(8,n) text into an HTML page, or use it as the value of the HTTP
       status:

           my $error(8,n) = $q->cgi_error;
           if(3,n) ($error(8,n)) {
               print $q->header(-status=>$error(8,n)),
                     $q->start_html('Problems'),
                     $q->h2('Request not processed'),
                     $q->strong($error(8,n));
               exit(3,n,1 builtins) 0;
           }

       When using the function-oriented interface (see the next section),
       errors may only occur the first time(1,2,n) you call param(). Be ready for
       this!

       USING THE FUNCTION-ORIENTED INTERFACE

       To use the function-oriented interface, you must specify which CGI.pm
       routines or sets of routines to import into your script's namespace.
       There is a small overhead associated with this importation, but it
       isn't much.

          use CGI <list of methods>;

       The listed methods will be imported into the current package; you can
       call them directly without creating a CGI object first.  This example
       shows how to import the param() and header() methods, and then use them
       directly:

          use CGI 'param','header';
          print header('text/plain');
          $zipcode = param('zipcode');

       More frequently, you'll import common sets of functions by referring to
       the groups by name.  All function sets are preceded with a ":" charac-
       ter as in(1,8) ":html3" (for tags defined in(1,8) the HTML 3 standard).

       Here is a list of the function sets you can import:

       :cgi
           Import all CGI-handling methods, such as param(), path_info() and
           the like.

       :form
           Import all fill-out form generating methods, such as textfield().

       :html2
           Import all methods that generate HTML 2.0 standard elements.

       :html3
           Import all methods that generate HTML 3.0 elements (such as <ta-
           ble>, <super> and <sub>).

       :html4
           Import all methods that generate HTML 4 elements (such as <abbrev>,
           <acronym> and <thead>).

       :netscape
           Import all methods that generate Netscape-specific HTML extensions.

       :html
           Import all HTML-generating shortcuts (i.e. 'html2' + 'html3' +
           'netscape')...

       :standard
           Import "standard" features, 'html2', 'html3', 'html4', 'form' and
           'cgi'.

       :all
           Import all the available methods.  For the full list, see the
           CGI.pm code, where the variable %EXPORT_TAGS is defined.

       If you import a function name that is not part of CGI.pm, the module
       will treat it as a new HTML tag and generate the appropriate subrou-
       tine.  You can then use it like any other HTML tag.  This is to provide
       for the rapidly-evolving HTML "standard."  For example, say Microsoft
       comes out with a new tag called <gradient> (which causes the user's
       desktop to be flooded with a rotating gradient fill until his machine
       reboots).  You don't need to wait for a new version(1,3,5) of CGI.pm to start
       using it immediately:

          use CGI qw/:standard :html3 gradient/;
          print gradient({-start=>'red',-end=>'blue'});

       Note that in(1,8) the interests of execution speed CGI.pm does not use the
       standard Exporter syntax for specifying load(7,n) symbols.  This may change
       in(1,8) the future.

       If you import any of the state-maintaining CGI or form-generating meth-
       ods, a default CGI object will be created and initialized automatically
       the first time(1,2,n) you use any of the methods that require one to be
       present.  This includes param(), textfield(), submit() and the like.
       (If you need direct access(2,5) to the CGI object, you can find it in(1,8) the
       global variable $CGI::Q).  By importing CGI.pm methods, you can create
       visually elegant scripts:

          use CGI qw/:standard/;
          print
              header,
              start_html('Simple Script'),
              h1('Simple Script'),
              start_form,
              "What's your name? ",textfield('name'),p,
              "What's the combination?",
              checkbox_group(-name=>'words',
                             -values=>['eenie','meenie','minie','moe'],
                             -defaults=>['eenie','moe']),p,
              "What's your favorite color?",
              popup_menu(-name=>'color',
                         -values=>['red','green','blue','chartreuse']),p,
              submit,
              end_form,
              hr,"\n";

           if(3,n) (param) {
              print
                  "Your name is ",em(param('name')),p,
                  "The keywords are: ",em(join(1,n)(", ",param('words'))),p,
                  "Your favorite color is ",em(param('color')),".\n";
           }
           print end_html;

       PRAGMAS

       In addition to the function sets, there are a number of pragmas that
       you can import.  Pragmas, which are always preceded by a hyphen, change
       the way that CGI.pm functions in(1,8) various ways.  Pragmas, function sets,
       and individual functions can all be imported in(1,8) the same use() line.
       For example, the following use statement imports the standard set(7,n,1 builtins) of
       functions and enables debugging mode (pragma -debug):

          use CGI qw/:standard -debug/;

       The current list of pragmas is as follows:

       -any
           When you use CGI -any, then any method that the query object
           doesn't recognize will be interpreted as a new HTML tag.  This
           allows you to support the next ad hoc Netscape or Microsoft HTML
           extension.  This lets you go wild with new and unsupported tags:

              use CGI qw(-any);
              $q=new CGI;
              print $q->gradient({speed=>'fast',start=>'red',end=>'blue'});

           Since using <cite>any</cite> causes any mistyped method name to be
           interpreted as an HTML tag, use it with care or not at all.

       -compile
           This causes the indicated autoloaded methods to be compiled up
           front, rather than deferred to later.  This is useful for scripts
           that run for an extended period of time(1,2,n) under FastCGI or mod_perl,
           and for those destined to be crunched by Malcom Beattie's Perl com-
           piler.  Use it in(1,8) conjunction with the methods or method families
           you plan to use.

              use CGI qw(-compile :standard :html3);

           or even

              use CGI qw(-compile :all);

           Note that using the -compile pragma in(1,8) this way will always have
           the effect of importing the compiled functions into the current
           namespace.  If you want to compile without importing use the com-
           pile() method instead:

              use CGI();
              CGI->compile();

           This is particularly useful in(1,8) a mod_perl environment, in(1,8) which you
           might want to precompile all CGI routines in(1,8) a startup script, and
           then import the functions individually in(1,8) each mod_perl script.

       -nosticky
           This makes CGI.pm not generating the hidden fields .submit and
           .cgifields. It is very useful if(3,n) you don't want to have the hidden
           fields appear in(1,8) the querystring in(1,8) a GET method.  For example, a
           search script generated this way will have a very nice(1,2) url with
           search parameters for bookmarking.

       -no_undef_params
           This keeps CGI.pm from including undef params in(1,8) the parameter
           list.

       -no_xhtml
           By default, CGI.pm versions 2.69 and higher emit XHTML
           (http://www.w3.org/TR/xhtml1/).  The -no_xhtml pragma disables this
           feature.  Thanks to Michalis Kabrianis <kabrianis@hellug.gr> for
           this feature.

           If start_html()'s -dtd parameter specifies an HTML 2.0 or 3.2 DTD,
           XHTML will automatically be disabled without needing to use this
           pragma.

       -nph
           This makes CGI.pm produce a header appropriate for an NPH (no
           parsed header) script.  You may need to do other things as well to
           tell the server that the script is NPH.  See the discussion of NPH
           scripts below.

       -newstyle_urls
           Separate the name=value pairs in(1,8) CGI parameter query strings with
           semicolons rather than ampersands.  For example:

              ?name=fred;age=24;favorite_color=3

           Semicolon-delimited query strings are always accepted, but will not
           be emitted by self_url() and query_string() unless the -new-
           style_urls pragma is specified.

           This became the default in(1,8) version(1,3,5) 2.64.

       -oldstyle_urls
           Separate the name=value pairs in(1,8) CGI parameter query strings with
           ampersands rather than semicolons.  This is no longer the default.

       -autoload
           This overrides the autoloader so that any function in(1,8) your program
           that is not recognized is referred to CGI.pm for possible evalua-
           tion.  This allows you to use all the CGI.pm functions without
           adding them to your symbol table, which is of concern for mod_perl
           users(1,5) who are worried about memory consumption.  Warning: when
           -autoload is in(1,8) effect, you cannot use "poetry mode" (functions
           without the parenthesis).  Use hr() rather than hr, or add some-
           thing like use subs qw/hr p header/ to the top of your script.

       -no_debug
           This turns off the command-line processing features.  If you want
           to run a CGI.pm script from the command line to produce HTML, and
           you don't want it to read(2,n,1 builtins) CGI parameters from the command line or
           STDIN, then use this pragma:

              use CGI qw(-no_debug :standard);

       -debug
           This turns on full debugging.  In addition to reading CGI arguments
           from the command-line processing, CGI.pm will pause and try to read(2,n,1 builtins)
           arguments from STDIN, producing the message "(offline mode: enter
           name=value pairs on standard input)" features.

           See the section on debugging for more details.

       -private_tempfiles
           CGI.pm can process uploaded file. Ordinarily it spools the uploaded
           file(1,n) to a temporary directory, then deletes the file(1,n) when done.
           However, this opens the risk of eavesdropping as described in(1,8) the
           file(1,n) upload section.  Another CGI script author could peek at this
           data during the upload, even if(3,n) it is confidential information. On
           Unix systems, the -private_tempfiles pragma will cause the tempo-
           rary file(1,n) to be unlinked as soon as it is opened and before any
           data is written into it, reducing, but not eliminating the risk of
           eavesdropping (there is still a potential race condition).  To make
           life harder for the attacker, the program chooses tempfile names by
           calculating a 32 bit checksum of the incoming HTTP headers.

           To ensure that the temporary file(1,n) cannot be read(2,n,1 builtins) by other CGI
           scripts, use suEXEC or a CGI wrapper program to run your script.
           The temporary file(1,n) is created with mode 0600 (neither world nor
           group readable).

           The temporary directory is selected using the following algorithm:

               1. if(3,n) the current user (e.g. "nobody") has a directory named(5,8)
               "tmp" in(1,8) its home directory, use that (Unix systems only).

               2. if(3,n) the environment variable TMPDIR exists, use the location
               indicated.

               3. Otherwise try the locations /usr/tmp, /var/tmp, C:\temp,
               /tmp, /temp, ::Temporary Items, and \WWW_ROOT.

           Each of these locations is checked that it is a directory and is
           writable.  If not, the algorithm tries the next choice.

       SPECIAL FORMS FOR IMPORTING HTML-TAG FUNCTIONS

       Many of the methods generate HTML tags.  As described below, tag func-
       tions automatically generate both the opening and closing tags.  For
       example:

         print h1('Level 1 Header');

       produces

         <h1>Level 1 Header</h1>

       There will be some times when you want to produce the start and end
       tags yourself.  In this case, you can use the form start_tag_name and
       end_tag_name, as in:

         print start_h1,'Level 1 Header',end_h1;

       With a few exceptions (described below), start_tag_name and
       end_tag_name functions are not generated automatically when you use
       CGI.  However, you can specify the tags you want to generate start/end
       functions for by putting an asterisk in(1,8) front of their name, or, alter-
       natively, requesting either "start_tag_name" or "end_tag_name" in(1,8) the
       import list.

       Example:

         use CGI qw/:standard *table start_ul/;

       In this example, the following functions are generated in(1,8) addition to
       the standard ones:

       1. start_table() (generates a <table> tag)
       2. end_table() (generates a </table> tag)
       3. start_ul() (generates a <ul> tag)
       4. end_ul() (generates a </ul> tag)

GENERATING DYNAMIC DOCUMENTS
       Most of CGI.pm's functions deal with creating documents on the fly.
       Generally you will produce the HTTP header first, followed by the docu-
       ment itself.  CGI.pm provides functions for generating HTTP headers of
       various types as well as for generating HTML.  For creating GIF images,
       see the GD.pm module.

       Each of these functions produces a fragment of HTML or HTTP which you
       can print out directly so that it displays in(1,8) the browser window,
       append to a string(3,n), or save to a file(1,n) for later use.

       CREATING A STANDARD HTTP HEADER:

       Normally the first thing you will do in(1,8) any CGI script is print out an
       HTTP header.  This tells the browser what type of document to expect,
       and gives other optional information, such as the language, expiration
       date, and whether to cache the document.  The header can also be manip-
       ulated for special purposes, such as server push and pay per view
       pages.

               print $query->header;

                    -or-

               print $query->header('image/gif');

                    -or-

               print $query->header('text/html','204 No response');

                    -or-

               print $query->header(-type=>'image/gif',
                                    -nph=>1,
                                    -status=>'402 Payment required',
                                    -expires=>'+3d',
                                    -cookie=>$cookie,
                                    -charset=>'utf-7',
                                    -attachment=>'foo.gif',
                                    -Cost=>'$2.00');

       header() returns the Content-type: header.  You can provide your own
       MIME type if(3,n) you choose, otherwise it defaults to text/html.  An
       optional second parameter specifies the status code and a human-read-
       able message.  For example, you can specify 204, "No response" to cre-
       ate a script that tells the browser to do nothing at all.

       The last example shows the named(5,8) argument style for passing arguments
       to the CGI methods using named(5,8) parameters.  Recognized parameters are
       -type, -status, -expires, and -cookie.  Any other named(5,8) parameters will
       be stripped of their initial hyphens and turned into header fields,
       allowing you to specify any HTTP header you desire.  Internal under-
       scores will be turned into hyphens:

           print $query->header(-Content_length=>3002);

       Most browsers will not cache the output from CGI scripts.  Every time(1,2,n)
       the browser reloads the page, the script is invoked anew.  You can
       change this behavior with the -expires parameter.  When you specify an
       absolute or relative expiration interval with this parameter, some
       browsers and proxy servers will cache the script's output until the
       indicated expiration date.  The following forms are all valid for the
       -expires field:

               +30s                              30 seconds from now
               +10m                              ten minutes from now
               +1h                               one hour from now
               -1d                               yesterday (i.e. "ASAP!")
               now                               immediately
               +3M                               in(1,8) three months
               +10y                              in(1,8) ten years time(1,2,n)
               Thursday, 25-Apr-1999 00:40:33 GMT  at the indicated time(1,2,n) & date

       The -cookie parameter generates a header that tells the browser to pro-
       vide a "magic(4,5) cookie" during all subsequent transactions with your
       script.  Netscape cookies have a special format that includes interest-
       ing attributes such as expiration time.  Use the cookie() method to
       create and retrieve session cookies.

       The -nph parameter, if(3,n) set(7,n,1 builtins) to a true value, will issue the correct
       headers to work with a NPH (no-parse-header) script.  This is important
       to use with certain servers that expect all their scripts to be NPH.

       The -charset parameter can be used to control the character set(7,n,1 builtins) sent to
       the browser.  If not provided, defaults to ISO-8859-1.  As a side
       effect, this sets the charset() method as well.

       The -attachment parameter can be used to turn the page into an attach-
       ment.  Instead of displaying the page, some browsers will prompt the
       user to save it to disk.  The value of the argument is the suggested
       name for the saved file.  In order for this to work, you may have to
       set(7,n,1 builtins) the -type to "application/octet-stream".

       The -p3p parameter will add a P3P tag to the outgoing header.  The
       parameter can be an arrayref or a space-delimited string(3,n) of P3P tags.
       For example:

          print header(-p3p=>[qw(CAO DSP LAW CURa)]);
          print header(-p3p=>'CAO DSP LAW CURa');

       In either case, the outgoing header will be formatted as:

         P3P: policyref="/w3c/p3p.xml" cp="CAO DSP LAW CURa"

       GENERATING A REDIRECTION HEADER

          print $query->redirect('http://somewhere.else/in(1,8)/movie/land');

       Sometimes you don't want to produce a document yourself, but simply re-
       direct the browser elsewhere, perhaps choosing a URL based on the time(1,2,n)
       of day or the identity of the user.

       The redirect() function redirects the browser to a different URL.  If
       you use redirection like this, you should not print out a header as
       well.

       You should always use full URLs (including the http: or ftp: part) in(1,8)
       redirection requests.  Relative URLs will not work correctly.

       You can also use named(5,8) arguments:

           print $query->redirect(-uri=>'http://somewhere.else/in(1,8)/movie/land',
                                  -nph=>1,
                                  -status=>301);

       The -nph parameter, if(3,n) set(7,n,1 builtins) to a true value, will issue the correct
       headers to work with a NPH (no-parse-header) script.  This is important
       to use with certain servers, such as Microsoft IIS, which expect all
       their scripts to be NPH.

       The -status parameter will set(7,n,1 builtins) the status of the redirect.  HTTP
       defines three different possible redirection status codes:

            301 Moved Permanently
            302 Found
            303 See Other

       The default if(3,n) not specified is 302, which means "moved temporarily."
       You may change the status to another status code if(3,n) you wish.  Be
       advised that changing the status to anything other than 301, 302 or 303
       will probably break redirection.

       CREATING THE HTML DOCUMENT HEADER

          print $query->start_html(-title=>'Secrets of the Pyramids',
                                   -author=>'fred@capricorn.org',
                                   -base=>'true',
                                   -target=>'_blank',
                                   -meta=>{'keywords'=>'pharaoh secret mummy',
                                           'copyright'=>'copyright 1996 King Tut'},
                                   -style=>{'src'=>'/styles/style1.css'},
                                   -BGCOLOR=>'blue');

       After creating the HTTP header, most CGI scripts will start writing out
       an HTML document.  The start_html() routine creates the top of the
       page, along with a lot of optional information that controls the page's
       appearance and behavior.

       This method returns a canned HTML header and the opening <body> tag.
       All parameters are optional.  In the named(5,8) parameter form, recognized
       parameters are -title, -author, -base, -xbase, -dtd, -lang and -target
       (see below for the explanation).  Any additional parameters you pro-
       vide, such as the Netscape unofficial BGCOLOR attribute, are added to
       the <body> tag.  Additional parameters must be proceeded by a hyphen.

       The argument -xbase allows you to provide an HREF for the <base> tag
       different from the current location, as in(1,8)

           -xbase=>"http://home.mcom.com/"

       All relative links will be interpreted relative to this tag.

       The argument -target allows you to provide a default target frame for
       all the links and fill-out forms on the page.  This is a non-standard
       HTTP feature which only works with Netscape browsers!  See the Netscape
       documentation on frames for details of how to manipulate this.

           -target=>"answer_window"

       All relative links will be interpreted relative to this tag.  You add
       arbitrary meta information to the header with the -meta argument.  This
       argument expects a reference to an associative array containing
       name/value pairs of meta information.  These will be turned into a
       series of header <meta> tags that look(1,8,3 Search::Dict) something like this:

           <meta name="keywords" content="pharaoh secret mummy">
           <meta name="description" content="copyright 1996 King Tut">

       To create an HTTP-EQUIV type of <meta> tag, use -head, described below.

       The -style argument is used to incorporate cascading stylesheets into
       your code.  See the section on CASCADING STYLESHEETS for more informa-
       tion.

       The -lang argument is used to incorporate a language attribute into the
       <html> tag.  For example:

           print $q->start_html(-lang=>'fr-CA');

       The default if(3,n) not specified is "en-US" for US English, unless the -dtd
       parameter specifies an HTML 2.0 or 3.2 DTD, in(1,8) which case the lang
       attribute is left off.  You can force the lang attribute to left off in(1,8)
       other cases by passing an empty string(3,n) (-lang=>'').

       The -encoding argument can be used to specify the character set(7,n,1 builtins) for
       XHTML.  It defaults to iso-8859-1 if(3,n) not specified.

       You can place other arbitrary HTML elements to the <head> section with
       the -head tag.  For example, to place the rarely-used <link(1,2)> element in(1,8)
       the head section, use this:

           print start_html(-head=>Link({-rel=>'next',
                                         -href=>'http://www.capricorn.com/s2.html'}));

       To incorporate multiple HTML elements into the <head> section, just
       pass an array reference:

           print start_html(-head=>[
                                    Link({-rel=>'next',
                                          -href=>'http://www.capricorn.com/s2.html'}),
                                    Link({-rel=>'previous',
                                          -href=>'http://www.capricorn.com/s1.html'})
                                    ]
                            );

       And here's how to create an HTTP-EQUIV <meta> tag:

             print start_html(-head=>meta({-http_equiv => 'Content-Type',
                                           -content    => 'text/html'}))

       JAVASCRIPTING: The -script, -noScript, -onLoad, -onMouseOver, -onMouse-
       Out and -onUnload parameters are used to add Netscape JavaScript calls
       to your pages.  -script should point to a block of text containing
       JavaScript function definitions.  This block will be placed within a
       <script> block inside the HTML (not HTTP) header.  The block is placed
       in(1,8) the header in(1,8) order to give your page a fighting chance of having
       all its JavaScript functions in(1,8) place even if(3,n) the user presses the stop
       button before the page has loaded completely.  CGI.pm attempts to for-
       mat the script in(1,8) such a way that JavaScript-naive browsers will not
       choke on the code: unfortunately there are some browsers, such as
       Chimera for Unix, that get confused by it nevertheless.

       The -onLoad and -onUnload parameters point to fragments of JavaScript
       code to execute when the page is respectively opened and closed by the
       browser.  Usually these parameters are calls to functions defined in(1,8)
       the -script field:

             $query = new CGI;
             print $query->header;
             $JSCRIPT=<<END;
             // Ask a silly question
             function riddle_me_this() {
                var r = prompt("What walks on four legs in(1,8) the morning, " +
                              "two legs in(1,8) the afternoon, " +
                              "and three legs in(1,8) the evening?");
                response(r);
             }
             // Get a silly answer
             function response(answer) {
                if(3,n) (answer == "man(1,5,7)")
                   alert("Right you are!");
                else
                   alert("Wrong!  Guess again.");
             }
             END
             print $query->start_html(-title=>'The Riddle of the Sphinx',
                                      -script=>$JSCRIPT);

       Use the -noScript parameter to pass some HTML text that will be dis-
       played on browsers that do not have JavaScript (or browsers where
       JavaScript is turned off).

       Netscape 3.0 recognizes several attributes of the <script> tag, includ-
       ing LANGUAGE and SRC.  The latter is particularly interesting, as it
       allows you to keep the JavaScript code in(1,8) a file(1,n) or CGI script rather
       than cluttering up each page with the source.  To use these attributes
       pass a HASH reference in(1,8) the -script parameter containing one or more
       of -language, -src, or -code:

           print $q->start_html(-title=>'The Riddle of the Sphinx',
                                -script=>{-language=>'JAVASCRIPT',
                                          -src=>'/javascript/sphinx.js'}
                                );

           print $q->(-title=>'The Riddle of the Sphinx',
                      -script=>{-language=>'PERLSCRIPT',
                                -code=>'print "hello world!\n;"'}
                      );

       A final feature allows you to incorporate multiple <script> sections
       into the header.  Just pass the list of script sections as an array
       reference.  this allows you to specify different source files for dif-
       ferent dialects of JavaScript.  Example:

            print $q->start_html(-title=>'The Riddle of the Sphinx',
                                 -script=>[
                                           { -language => 'JavaScript1.0',
                                             -src      => '/javascript/utilities10.js'
                                           },
                                           { -language => 'JavaScript1.1',
                                             -src      => '/javascript/utilities11.js'
                                           },
                                           { -language => 'JavaScript1.2',
                                             -src      => '/javascript/utilities12.js'
                                           },
                                           { -language => 'JavaScript28.2',
                                             -src      => '/javascript/utilities219.js'
                                           }
                                        ]
                                    );

       If this looks a bit extreme, take my advice and stick with straight CGI
       scripting.

       See

          http://home.netscape.com/eng/mozilla/2.0/handbook/javascript/

       for more information about JavaScript.

       The old-style positional parameters are as follows:

       Parameters:
       1.  The title

       2.  The author's e-mail address (will create a <link(1,2) rev="MADE"> tag if(3,n)
           present

       3.  A 'true' flag if(3,n) you want to include a <base> tag in(1,8) the header.
           This helps resolve relative addresses to absolute ones when the
           document is moved, but makes the document hierarchy non-portable.
           Use with care!

       4, 5, 6...
           Any other parameters you want to include in(1,8) the <body> tag.  This
           is a good place to put Netscape extensions, such as colors and
           wallpaper patterns.

       ENDING THE HTML DOCUMENT:

               print $query->end_html

       This ends an HTML document by printing the </body></html> tags.

       CREATING A SELF-REFERENCING URL THAT PRESERVES STATE INFORMATION:

           $myself = $query->self_url;
           print q(<a href="$myself">I'm talking to myself.</a>);

       self_url() will return a URL, that, when selected, will reinvoke this
       script with all its state information intact.  This is most useful when
       you want to jump around within the document using internal anchors but
       you don't want to disrupt the current contents of the form(s).  Some-
       thing like this will do the trick.

            $myself = $query->self_url;
            print "<a href=\"$myself#table1\">See table 1</a>";
            print "<a href=\"$myself#table2\">See table 2</a>";
            print "<a href=\"$myself#yourself\">See for yourself</a>";

       If you want more control over what's returned, using the url() method
       instead.

       You can also retrieve the unprocessed query string(3,n) with query_string():

           $the_string = $query->query_string;

       OBTAINING THE SCRIPT'S URL

           $full_url      = $query->url();
           $full_url      = $query->url(-full=>1);  #alternative syntax
           $relative_url  = $query->url(-relative=>1);
           $absolute_url  = $query->url(-absolute=>1);
           $url_with_path = $query->url(-path_info=>1);
           $url_with_path_and_query = $query->url(-path_info=>1,-query=>1);
           $netloc        = $query->url(-base => 1);

       url() returns the script's URL in(1,8) a variety of formats.  Called without
       any arguments, it returns the full form of the URL, including host(1,5) name
       and port number

           http://your.host.com/path/to/script.cgi

       You can modify this format with the following named(5,8) arguments:

       -absolute
           If true, produce an absolute URL, e.g.

               /path/to/script.cgi

       -relative
           Produce a relative URL.  This is useful if(3,n) you want to reinvoke
           your script with different parameters. For example:

               script.cgi

       -full
           Produce the full URL, exactly as if(3,n) called without any arguments.
           This overrides the -relative and -absolute arguments.

       -path (-path_info)
           Append the additional path information to the URL.  This can be
           combined with -full, -absolute or -relative.  -path_info is pro-
           vided as a synonym.

       -query (-query_string)
           Append the query string(3,n) to the URL.  This can be combined with
           -full, -absolute or -relative.  -query_string is provided as a syn-
           onym.

       -base
           Generate just the protocol and net location, as in(1,8)
           http://www.foo.com:8000

       MIXING POST AND URL PARAMETERS

          $color = $query->url_param('color');

       It is possible for a script to receive CGI parameters in(1,8) the URL as
       well as in(1,8) the fill-out form by creating a form that POSTs to a URL
       containing a query string(3,n) (a "?" mark followed by arguments).  The
       param() method will always return the contents of the POSTed fill-out
       form, ignoring the URL's query string.  To retrieve URL parameters,
       call the url_param() method.  Use it in(1,8) the same way as param().  The
       main difference is that it allows you to read(2,n,1 builtins) the parameters, but not
       set(7,n,1 builtins) them.

       Under no circumstances will the contents of the URL query string(3,n) inter-
       fere with similarly-named CGI parameters in(1,8) POSTed forms.  If you try
       to mix a URL query string(3,n) with a form submitted with the GET method,
       the results will not be what you expect.

CREATING STANDARD HTML ELEMENTS:
       CGI.pm defines general HTML shortcut methods for most, if(3,n) not all of
       the HTML 3 and HTML 4 tags.  HTML shortcuts are named(5,8) after a single
       HTML element and return a fragment of HTML text that you can then print
       or manipulate as you like.  Each shortcut returns a fragment of HTML
       code that you can append to a string(3,n), save to a file(1,n), or, most com-
       monly, print out so that it displays in(1,8) the browser window.

       This example shows how to use the HTML methods:

          $q = new CGI;
          print $q->blockquote(
                            "Many years ago on the island of",
                            $q->a({href=>"http://crete.org/"},"Crete"),
                            "there lived a Minotaur named(5,8)",
                            $q->strong("Fred."),
                           ),
              $q->hr;

       This results in(1,8) the following HTML code (extra newlines have been added
       for readability):

          <blockquote>
          Many years ago on the island of
          <a href="http://crete.org/">Crete</a> there lived
          a minotaur named(5,8) <strong>Fred.</strong>
          </blockquote>
          <hr>

       If you find the syntax for calling the HTML shortcuts awkward, you can
       import them into your namespace and dispense with the object syntax
       completely (see the next section for more details):

          use CGI ':standard';
          print blockquote(
             "Many years ago on the island of",
             a({href=>"http://crete.org/"},"Crete"),
             "there lived a minotaur named(5,8)",
             strong("Fred."),
             ),
             hr;

       PROVIDING ARGUMENTS TO HTML SHORTCUTS

       The HTML methods will accept(2,8) zero, one or multiple arguments.  If you
       provide no arguments, you get a single tag:

          print hr;    #  <hr>

       If you provide one or more string(3,n) arguments, they are concatenated
       together with spaces and placed between opening and closing tags:

          print h1("Chapter","1"); # <h1>Chapter 1</h1>"

       If the first argument is an associative array reference, then the keys
       and values of the associative array become the HTML tag's attributes:

          print a({-href=>'fred.html',-target=>'_new'},
             "Open a new frame");

                   <a href="fred.html",target="_new">Open a new frame</a>

       You may dispense with the dashes in(1,8) front of the attribute names if(3,n) you
       prefer:

          print img {src=>'fred.gif',align=>'LEFT'};

                  <img align="LEFT" src="fred.gif">

       Sometimes an HTML tag attribute has no argument.  For example, ordered
       lists can be marked as COMPACT.  The syntax for this is an argument
       that that points to an undef string:

          print ol({compact=>undef},li('one'),li('two'),li('three'));

       Prior to CGI.pm version(1,3,5) 2.41, providing an empty ('') string(3,n) as an
       attribute argument was the same as providing undef.  However, this has
       changed in(1,8) order to accommodate those who want to create tags of the
       form <img alt="">.  The difference is shown in(1,8) these two pieces of
       code:

          CODE                   RESULT
          img({alt=>undef})      <img alt>
          img({alt=>''})         <img alt="">

       THE DISTRIBUTIVE PROPERTY OF HTML SHORTCUTS

       One of the cool features of the HTML shortcuts is that they are dis-
       tributive.  If you give them an argument consisting of a reference to a
       list, the tag will be distributed across each element of the list.  For
       example, here's one way to make an ordered list:

          print ul(
                    li({-type=>'disc'},['Sneezy','Doc','Sleepy','Happy'])
                  );

       This example will result in(1,8) HTML output that looks like this:

          <ul>
            <li type="disc">Sneezy</li>
            <li type="disc">Doc</li>
            <li type="disc">Sleepy</li>
            <li type="disc">Happy</li>
          </ul>

       This is extremely useful for creating tables.  For example:

          print table({-border=>undef},
                  caption('When Should You Eat Your Vegetables?'),
                  Tr({-align=>CENTER,-valign=>TOP},
                  [
                     th(['Vegetable', 'Breakfast','Lunch','Dinner']),
                     td(['Tomatoes' , 'no', 'yes', 'yes']),
                     td(['Broccoli' , 'no', 'no',  'yes']),
                     td(['Onions'   , 'yes','yes', 'yes'])
                  ]
                  )
               );

       HTML SHORTCUTS AND LIST INTERPOLATION

       Consider this bit of code:

          print blockquote(em('Hi'),'mom!'));

       It will ordinarily return the string(3,n) that you probably expect, namely:

          <blockquote><em>Hi</em> mom!</blockquote>

       Note the space between the element "Hi" and the element "mom!".  CGI.pm
       puts(3,n) the extra space there using array interpolation, which is con-
       trolled by the magic(4,5) $" variable.  Sometimes this extra space is not
       what you want, for example, when you are trying to align a series of
       images.  In this case, you can simply change the value of $" to an
       empty string.

          {
             local($") = '';
             print blockquote(em('Hi'),'mom!'));
           }

       I suggest you put the code in(1,8) a block as shown here.  Otherwise the
       change to $" will affect all subsequent code until you explicitly reset(1,7,1 tput)
       it.

       NON-STANDARD HTML SHORTCUTS

       A few HTML tags don't follow the standard pattern for various reasons.

       comment() generates an HTML comment (<!-- comment -->).  Call it like

           print comment('here is my comment');

       Because of conflicts with built-in Perl functions, the following func-
       tions begin with initial caps:

           Select
           Tr
           Link
           Delete
           Accept
           Sub

       In addition, start_html(), end_html(), start_form(), end_form(),
       start_multipart_form() and all the fill-out form tags are special.  See
       their respective sections.

       AUTOESCAPING HTML

       By default, all HTML that is emitted by the form-generating functions
       is passed through a function called escapeHTML():

       $escaped_string = escapeHTML("unescaped string(3,n)");
           Escape HTML formatting characters in(1,8) a string.

       Provided that you have specified a character set(7,n,1 builtins) of ISO-8859-1 (the
       default), the standard HTML escaping rules will be used.  The "<" char-
       acter becomes "&lt;", ">" becomes "&gt;", "&" becomes "&amp;", and the
       quote character becomes "&quot;".  In addition, the hexadecimal 0x8b
       and 0x9b characters, which some browsers incorrectly interpret as the
       left and right angle-bracket characters, are replaced by their numeric
       character entities ("&#8249" and "&#8250;").  If you manually change
       the charset, either by calling the charset() method explicitly or by
       passing a -charset argument to header(), then all characters will be
       replaced by their numeric entities, since CGI.pm has no lookup table
       for all the possible encodings.

       The automatic escaping does not apply to other shortcuts, such as h1().
       You should call escapeHTML() yourself on untrusted data in(1,8) order to
       protect your pages against nasty tricks that people may enter into
       guestbooks, etc..  To change the character set(7,n,1 builtins), use charset().  To turn
       autoescaping off completely, use autoEscape(0):

       $charset = charset([$charset]);
           Get or set(7,n,1 builtins) the current character set.

       $flag = autoEscape([$flag]);
           Get or set(7,n,1 builtins) the value of the autoescape flag.

       PRETTY-PRINTING HTML

       By default, all the HTML produced by these functions comes out as one
       long line without carriage returns or indentation. This is yuck, but it
       does reduce the size of the documents by 10-20%.  To get pretty-printed
       output, please use CGI::Pretty, a subclass contributed by Brian
       Paulsen.

CREATING FILL-OUT FORMS:
       General note  The various form-creating methods all return strings to
       the caller, containing the tag or tags that will create the requested
       form element.  You are responsible for actually printing out these
       strings.  It's set(7,n,1 builtins) up this way so that you can place formatting tags
       around the form elements.

       Another note The default values that you specify for the forms are only
       used the first time(1,2,n) the script is invoked (when there is no query
       string(3,n)).  On subsequent invocations of the script (when there is a
       query string(3,n)), the former values are used even if(3,n) they are blank.

       If you want to change the value of a field from its previous value, you
       have two choices:

       (1) call the param() method to set(7,n,1 builtins) it.

       (2) use the -override (alias -force) parameter (a new feature in(1,8) ver-
       sion(1,3,5) 2.15).  This forces the default value to be used, regardless of
       the previous value:

          print $query->textfield(-name=>'field_name',
                                  -default=>'starting value',
                                  -override=>1,
                                  -size=>50,
                                  -maxlength=>80);

       Yet another note By default, the text and labels of form elements are
       escaped according to HTML rules.  This means that you can safely use
       "<CLICK ME>" as the label for a button.  However, it also interferes
       with your ability to incorporate special HTML character sequences, such
       as &Aacute;, into your fields.  If you wish to turn off automatic
       escaping, call the autoEscape() method with a false value immediately
       after creating the CGI object:

          $query = new CGI;
          $query->autoEscape(undef);

       A Lurking Trap! Some of the form-element generating methods return mul-
       tiple tags.  In a scalar context, the tags will be concatenated
       together with spaces, or whatever is the current value of the $"
       global.  In a list context, the methods will return a list of elements,
       allowing you to modify them if(3,n) you wish.  Usually you will not notice
       this behavior, but beware of this:

           printf(1,3,1 builtins)("%s\n",$query->end_form())

       end_form() produces several tags, and only the first of them will be
       printed because the format only expects one value.

       <p>

       CREATING AN ISINDEX TAG

          print $query->isindex(-action=>$action);

                -or-

          print $query->isindex($action);

       Prints out an <isindex> tag.  Not very exciting.  The parameter -action
       specifies the URL of the script to process the query.  The default is
       to process the query with the current script.

       STARTING AND ENDING A FORM

           print $query->start_form(-method=>$method,
                                   -action=>$action,
                                   -enctype=>$encoding(3,n));
             <... various form stuff ...>
           print $query->endform;

               -or-

           print $query->start_form($method,$action,$encoding(3,n));
             <... various form stuff ...>
           print $query->endform;

       start_form() will return a <form> tag with the optional method, action
       and form encoding(3,n) that you specify.  The defaults are:

           method: POST
           action: this script
           enctype: application/x-www-form-urlencoded

       endform() returns the closing </form> tag.

       Start_form()'s enctype argument tells the browser how to package the
       various fields of the form before sending the form to the server.  Two
       values are possible:

       Note: This method was previously named(5,8) startform(), and startform() is
       still recognized as an alias.

       application/x-www-form-urlencoded
           This is the older type of encoding(3,n) used by all browsers prior to
           Netscape 2.0.  It is compatible with many CGI scripts and is suit-
           able for short fields containing text data.  For your convenience,
           CGI.pm stores the name of this encoding(3,n) type in(1,8) &CGI::URL_ENCODED.

       multipart/form-data
           This is the newer type of encoding(3,n) introduced by Netscape 2.0.  It
           is suitable for forms that contain very large fields or that are
           intended for transferring binary data.  Most importantly, it
           enables the "file(1,n) upload" feature of Netscape 2.0 forms.  For your
           convenience, CGI.pm stores the name of this encoding(3,n) type in(1,8)
           &CGI::MULTIPART

           Forms that use this type of encoding(3,n) are not easily interpreted by
           CGI scripts unless they use CGI.pm or another library designed to
           handle them.

       For compatibility, the start_form() method uses the older form of
       encoding(3,n) by default.  If you want to use the newer form of encoding(3,n) by
       default, you can call start_multipart_form() instead of start_form().

       JAVASCRIPTING: The -name and -onSubmit parameters are provided for use
       with JavaScript.  The -name parameter gives the form a name so that it
       can be identified and manipulated by JavaScript functions.  -onSubmit
       should point to a JavaScript function that will be executed just before
       the form is submitted to your server.  You can use this opportunity to
       check the contents of the form for consistency and completeness.  If
       you find something wrong, you can put up an alert box or maybe fix
       things up yourself.  You can abort(3,7) the submission by returning false
       from this function.

       Usually the bulk of JavaScript functions are defined in(1,8) a <script>
       block in(1,8) the HTML header and -onSubmit points to one of these function
       call.  See start_html() for details.

       CREATING A TEXT FIELD

           print $query->textfield(-name=>'field_name',
                                   -default=>'starting value',
                                   -size=>50,
                                   -maxlength=>80);
               -or-

           print $query->textfield('field_name','starting value',50,80);

       textfield() will return a text input field.

       Parameters
       1.  The first parameter is the required name for the field (-name).

       2.  The optional second parameter is the default starting value for the
           field contents (-default).

       3.  The optional third parameter is the size of the field in(1,8)
                 characters (-size).

       4.  The optional fourth parameter is the maximum number of characters
           the
                 field will accept(2,8) (-maxlength).

       As with all these methods, the field will be initialized with its pre-
       vious contents from earlier invocations of the script.  When the form
       is processed, the value of the text field can be retrieved with:

              $value = $query->param('foo');

       If you want to reset(1,7,1 tput) it from its initial value after the script has
       been called once, you can do so like this:

              $query->param('foo',"I'm taking over this value!");

       NEW AS OF VERSION 2.15: If you don't want the field to take on its pre-
       vious value, you can force its current value by using the -override
       (alias -force) parameter:

           print $query->textfield(-name=>'field_name',
                                   -default=>'starting value',
                                   -override=>1,
                                   -size=>50,
                                   -maxlength=>80);

       JAVASCRIPTING: You can also provide -onChange, -onFocus, -onBlur,
       -onMouseOver, -onMouseOut and -onSelect parameters to register
       JavaScript event handlers.  The onChange handler will be called when-
       ever the user changes the contents of the text field.  You can do text
       validation if(3,n) you like.  onFocus and onBlur are called respectively
       when the insertion point moves into and out of the text field.  onSe-
       lect is called when the user changes the portion of the text that is
       selected.

       CREATING A BIG TEXT FIELD

          print $query->textarea(-name=>'foo',
                                 -default=>'starting value',
                                 -rows=>10,
                                 -columns=>50);

               -or

          print $query->textarea('foo','starting value',10,50);

       textarea() is just like textfield, but it allows you to specify rows
       and columns for a multiline text entry box.  You can provide a starting
       value for the field, which can be long and contain multiple lines.

       JAVASCRIPTING: The -onChange, -onFocus, -onBlur , -onMouseOver,
       -onMouseOut, and -onSelect parameters are recognized.  See textfield().

       CREATING A PASSWORD FIELD

          print $query->password_field(-name=>'secret',
                                       -value=>'starting value',
                                       -size=>50,
                                       -maxlength=>80);
               -or-

          print $query->password_field('secret','starting value',50,80);

       password_field() is identical to textfield(), except that its contents
       will be starred out on the web page.

       JAVASCRIPTING: The -onChange, -onFocus, -onBlur, -onMouseOver,
       -onMouseOut and -onSelect parameters are recognized.  See textfield().

       CREATING A FILE UPLOAD FIELD

           print $query->filefield(-name=>'uploaded_file',
                                   -default=>'starting value',
                                   -size=>50,
                                   -maxlength=>80);
               -or-

           print $query->filefield('uploaded_file','starting value',50,80);

       filefield() will return a file(1,n) upload field for Netscape 2.0 browsers.
       In order to take full advantage of this you must use the new multipart
       encoding(3,n) scheme for the form.  You can do this either by calling
       start_form() with an encoding(3,n) type of &CGI::MULTIPART, or by calling
       the new method start_multipart_form() instead of vanilla start_form().

       Parameters
       1.  The first parameter is the required name for the field (-name).

       2.  The optional second parameter is the starting value for the field
           contents to be used as the default file(1,n) name (-default).

           For security reasons, browsers don't pay any attention to this
           field, and so the starting value will always be blank.  Worse, the
           field loses its "sticky" behavior and forgets its previous con-
           tents.  The starting value field is called for in(1,8) the HTML specifi-
           cation, however, and possibly some browser will eventually provide
           support for it.

       3.  The optional third parameter is the size of the field in(1,8) characters
           (-size).

       4.  The optional fourth parameter is the maximum number of characters
           the field will accept(2,8) (-maxlength).

       When the form is processed, you can retrieve the entered filename by
       calling param():

              $filename = $query->param('uploaded_file');

       Different browsers will return slightly different things for the name.
       Some browsers return the filename only.  Others return the full path to
       the file(1,n), using the path conventions of the user's machine.  Regard-
       less(1,3), the name returned is always the name of the file(1,n) on the user's
       machine, and is unrelated to the name of the temporary file(1,n) that CGI.pm
       creates during upload spooling (see below).

       The filename returned is also a file(1,n) handle.  You can read(2,n,1 builtins) the contents
       of the file(1,n) using standard Perl file(1,n) reading calls:

               # Read a text file(1,n) and print it out
               while (<$filename>) {
                  print;
               }

               # Copy a binary file(1,n) to somewhere safe
               open(2,3,n) (OUTFILE,">>/usr/local/web/users(1,5)/feedback");
               while ($bytesread=read(2,n,1 builtins)($filename,$buffer,1024)) {
                  print OUTFILE $buffer;
               }

       However, there are problems with the dual nature of the upload fields.
       If you "use strict", then Perl will complain when you try to use a
       string(3,n) as a filehandle.  You can get around this by placing the file(1,n)
       reading code in(1,8) a block containing the "no strict" pragma.  More seri-
       ously, it is possible for the remote user to type garbage into the
       upload field, in(1,8) which case what you get from param() is not a filehan-
       dle at all, but a string.

       To be safe, use the upload() function (new in(1,8) version(1,3,5) 2.47).  When
       called with the name of an upload field, upload() returns a filehandle,
       or undef if(3,n) the parameter is not a valid filehandle.

            $fh = $query->upload('uploaded_file');
            while (<$fh>) {
                  print;
            }

       In an list context, upload() will return an array of filehandles.  This
       makes it possible to create forms that use the same name for multiple
       upload fields.

       This is the recommended idiom.

       When a file(1,n) is uploaded the browser usually sends along some informa-
       tion along with it in(1,8) the format of headers.  The information usually
       includes the MIME content type.  Future browsers may send(2,n) other infor-
       mation as well (such as modification date and size). To retrieve this
       information, call uploadInfo().  It returns a reference to an associa-
       tive array containing all the document headers.

              $filename = $query->param('uploaded_file');
              $type = $query->uploadInfo($filename)->{'Content-Type'};
              unless ($type eq 'text/html') {
                 die "HTML FILES ONLY!";
              }

       If you are using a machine that recognizes "text" and "binary" data
       modes, be sure to understand when and how to use them (see the Camel
       book).  Otherwise you may find that binary files are corrupted during
       file(1,n) uploads.

       There are occasionally problems involving parsing the uploaded file.
       This usually happens when the user presses "Stop" before the upload is
       finished.  In this case, CGI.pm will return undef for the name of the
       uploaded file(1,n) and set(7,n,1 builtins) cgi_error() to the string(3,n) "400 Bad request (mal-
       formed multipart POST)".  This error(8,n) message is designed so that you
       can incorporate it into a status code to be sent to the browser.  Exam-
       ple:

          $file(1,n) = $query->upload('uploaded_file');
          if(3,n) (!$file(1,n) && $query->cgi_error) {
             print $query->header(-status=>$query->cgi_error);
             exit(3,n,1 builtins) 0;
          }

       You are free to create a custom HTML page to complain about the error(8,n),
       if(3,n) you wish.

       You can set(7,n,1 builtins) up a callback that will be called whenever a file(1,n) upload is
       being read(2,n,1 builtins) during the form processing. This is much like the
       UPLOAD_HOOK facility available in(1,8) Apache::Request, with the exception
       that the first argument to the callback is an Apache::Upload object,
       here it's the remote filename.

        $q = CGI->new();
        $q->upload_hook(\&hook,$data);

        sub hook
        {
               my ($filename, $buffer, $bytes_read, $data) = @_;
               print  "Read $bytes_read bytes of $filename\n";
        }

       If using the function-oriented interface, call the CGI::upload_hook()
       method before calling param() or any other CGI functions:

         CGI::upload_hook(\&hook,$data);

       This method is not exported by default.  You will have to import it
       explicitly if(3,n) you wish to use it without the CGI:: prefix.

       If you are using CGI.pm on a Windows platform and find that binary
       files get slightly larger when uploaded but that text files remain the
       same, then you have forgotten to activate binary mode on the output
       filehandle.  Be sure to call binmode() on any handle that you create to
       write(1,2) the uploaded file(1,n) to disk.

       JAVASCRIPTING: The -onChange, -onFocus, -onBlur, -onMouseOver,
       -onMouseOut and -onSelect parameters are recognized.  See textfield()
       for details.

       CREATING A POPUP MENU

          print $query->popup_menu('menu_name',
                                   ['eenie','meenie','minie'],
                                   'meenie');

             -or-

          %labels = ('eenie'=>'your first choice',
                     'meenie'=>'your second choice',
                     'minie'=>'your third choice');
          %attributes = ('eenie'=>{'class'=>'class of first choice'});
          print $query->popup_menu('menu_name',
                                   ['eenie','meenie','minie'],
                 'meenie',\%labels,\%attributes);

               -or (named(5,8) parameter style)-

          print $query->popup_menu(-name=>'menu_name',
                                   -values=>['eenie','meenie','minie'],
                                   -default=>'meenie',
                 -labels=>\%labels,
                 -attributes=>\%attributes);

       popup_menu() creates a menu.

       1.  The required first argument is the menu(3x,n,n tk_menuSetFocus)'s name (-name).

       2.  The required second argument (-values) is an array reference con-
           taining the list of menu(3x,n,n tk_menuSetFocus) items in(1,8) the menu.  You can pass the
           method an anonymous array, as shown in(1,8) the example, or a reference
           to a named(5,8) array, such as "\@foo".

       3.  The optional third parameter (-default) is the name of the default
           menu(3x,n,n tk_menuSetFocus) choice.  If not specified, the first item will be the default.
           The values of the previous choice will be maintained across
           queries.

       4.  The optional fourth parameter (-labels) is provided for people who
           want to use different values for the user-visible label inside the
           popup menu(3x,n,n tk_menuSetFocus) and the value returned to your script.  It's a pointer
           to an associative array relating menu(3x,n,n tk_menuSetFocus) values to user-visible
           labels.  If you leave this parameter blank, the menu(3x,n,n tk_menuSetFocus) values will be
           displayed by default.  (You can also leave a label undefined if(3,n) you
           want to).

       5.  The optional fifth parameter (-attributes) is provided to assign
           any of the common HTML attributes to an individual menu(3x,n,n tk_menuSetFocus) item. It's
           a pointer to an associative array relating menu(3x,n,n tk_menuSetFocus) values to another
           associative array with the attribute's name as the key and the
           attribute's value as the value.

       When the form is processed, the selected value of the popup menu(3x,n,n tk_menuSetFocus) can be
       retrieved using:

             $popup_menu_value = $query->param('menu_name');

       JAVASCRIPTING: popup_menu() recognizes the following event handlers:
       -onChange, -onFocus, -onMouseOver, -onMouseOut, and -onBlur.  See the
       textfield() section for details on when these handlers are called.

       CREATING AN OPTION GROUP

       Named parameter style

         print $query->popup_menu(-name=>'menu_name',
                         -values=>[qw/eenie meenie minie/,
                                   $q->optgroup(-name=>'optgroup_name',
                                                -values ['moe','catch'],
                                                -attributes=>{'catch'=>{'class'=>'red'}}),
                         -labels=>{'eenie'=>'one',
                                   'meenie'=>'two',
                                   'minie'=>'three'},
                         -default=>'meenie');

         Old style
         print $query->popup_menu('menu_name',
                         ['eenie','meenie','minie',
                          $q->optgroup('optgroup_name', ['moe', 'catch'],
                                {'catch'=>{'class'=>'red'}})],'meenie',
                         {'eenie'=>'one','meenie'=>'two','minie'=>'three'});

       optgroup creates an option group within a popup menu.

       1.  The required first argument (-name) is the label attribute of the
           optgroup and is not inserted in(1,8) the parameter list of the query.

       2.  The required second argument (-values)  is an array reference con-
           taining the list of menu(3x,n,n tk_menuSetFocus) items in(1,8) the menu.  You can pass the
           method an anonymous array, as shown in(1,8) the example, or a reference
           to a named(5,8) array, such as \@foo.  If you pass a HASH reference, the
           keys will be used for the menu(3x,n,n tk_menuSetFocus) values, and the values will be used
           for the menu(3x,n,n tk_menuSetFocus) labels (see -labels below).

       3.  The optional third parameter (-labels) allows you to pass a refer-
           ence to an associative array containing user-visible labels for one
           or more of the menu(3x,n,n tk_menuSetFocus) items.  You can use this when you want the user
           to see one menu(3x,n,n tk_menuSetFocus) string(3,n), but have the browser return your program a
           different one.  If you don't specify this, the value string(3,n) will be
           used instead ("eenie", "meenie" and "minie" in(1,8) this example).  This
           is equivalent to using a hash reference for the -values parameter.

       4.  An optional fourth parameter (-labeled) can be set(7,n,1 builtins) to a true value
           and indicates that the values should be used as the label attribute
           for each option element within the optgroup.

       5.  An optional fifth parameter (-novals) can be set(7,n,1 builtins) to a true value
           and indicates to suppress the val attribut in(1,8) each option element
           within the optgroup.

           See the discussion on optgroup at W3C
           (http://www.w3.org/TR/REC-html40/interact/forms.html#edef-OPTGROUP)
           for details.

       6.  An optional sixth parameter (-attributes) is provided to assign any
           of the common HTML attributes to an individual menu(3x,n,n tk_menuSetFocus) item. It's a
           pointer to an associative array relating menu(3x,n,n tk_menuSetFocus) values to another
           associative array with the attribute's name as the key and the
           attribute's value as the value.

       CREATING A SCROLLING LIST

          print $query->scrolling_list('list_name',
                                       ['eenie','meenie','minie','moe'],
               ['eenie','moe'],5,'true',{'moe'=>{'class'=>'red'}});
             -or-

          print $query->scrolling_list('list_name',
                                       ['eenie','meenie','minie','moe'],
                                       ['eenie','moe'],5,'true',
               \%labels,%attributes);

               -or-

          print $query->scrolling_list(-name=>'list_name',
                                       -values=>['eenie','meenie','minie','moe'],
                                       -default=>['eenie','moe'],
                                       -size=>5,
                                       -multiple=>'true',
               -labels=>\%labels,
               -attributes=>\%attributes);

       scrolling_list() creates a scrolling list.

       Parameters:
       1.  The first and second arguments are the list name (-name) and values
           (-values).  As in(1,8) the popup menu(3x,n,n tk_menuSetFocus), the second argument should be an
           array reference.

       2.  The optional third argument (-default) can be either a reference to
           a list containing the values to be selected by default, or can be a
           single value to select.  If this argument is missing or undefined,
           then nothing is selected when the list first appears.  In the named(5,8)
           parameter version(1,3,5), you can use the synonym "-defaults" for this
           parameter.

       3.  The optional fourth argument is the size of the list (-size).

       4.  The optional fifth argument can be set(7,n,1 builtins) to true to allow multiple
           simultaneous selections (-multiple).  Otherwise only one selection
           will be allowed at a time.

       5.  The optional sixth argument is a pointer to an associative array
           containing long user-visible labels for the list items (-labels).
           If not provided, the values will be displayed.

       6.  The optional sixth parameter (-attributes) is provided to assign
           any of the common HTML attributes to an individual menu(3x,n,n tk_menuSetFocus) item. It's
           a pointer to an associative array relating menu(3x,n,n tk_menuSetFocus) values to another
           associative array with the attribute's name as the key and the
           attribute's value as the value.

           When this form is processed, all selected list items will be
           returned as a list under the parameter name 'list_name'.  The val-
           ues of the selected items can be retrieved with:

                 @selected = $query->param('list_name');

       JAVASCRIPTING: scrolling_list() recognizes the following event han-
       dlers: -onChange, -onFocus, -onMouseOver, -onMouseOut and -onBlur.  See
       textfield() for the description of when these handlers are called.

       CREATING A GROUP OF RELATED CHECKBOXES

          print $query->checkbox_group(-name=>'group_name',
                                       -values=>['eenie','meenie','minie','moe'],
                                       -default=>['eenie','moe'],
                                       -linebreak=>'true',
               -labels=>\%labels,
               -attributes=>\%attributes);

          print $query->checkbox_group('group_name',
                                       ['eenie','meenie','minie','moe'],
               ['eenie','moe'],'true',\%labels,
               {'moe'=>{'class'=>'red'}});

          HTML3-COMPATIBLE BROWSERS ONLY:

          print $query->checkbox_group(-name=>'group_name',
                                       -values=>['eenie','meenie','minie','moe'],
                                       -rows=2,-columns=>2);

       checkbox_group() creates a list of checkboxes that are related by the
       same name.

       Parameters:
       1.  The first and second arguments are the checkbox name and values,
           respectively (-name and -values).  As in(1,8) the popup menu(3x,n,n tk_menuSetFocus), the second
           argument should be an array reference.  These values are used for
           the user-readable labels printed next to the checkboxes as well as
           for the values passed to your script in(1,8) the query string.

       2.  The optional third argument (-default) can be either a reference to
           a list containing the values to be checked by default, or can be a
           single value to checked.  If this argument is missing or undefined,
           then nothing is selected when the list first appears.

       3.  The optional fourth argument (-linebreak) can be set(7,n,1 builtins) to true to
           place line breaks between the checkboxes so that they appear as a
           vertical list.  Otherwise, they will be strung together on a hori-
           zontal line.

       4.  The optional fifth argument is a pointer to an associative array
           relating the checkbox values to the user-visible labels that will
           be printed next to them (-labels).  If not provided, the values
           will be used as the default.

       5.  HTML3-compatible browsers (such as Netscape) can take advantage of
           the optional parameters -rows, and -columns.  These parameters
           cause checkbox_group() to return an HTML3 compatible table contain-
           ing the checkbox group formatted with the specified number of rows
           and columns.  You can provide just the -columns parameter if(3,n) you
           wish; checkbox_group will calculate the correct number of rows for
           you.

       6.  The optional sixth parameter (-attributes) is provided to assign
           any of the common HTML attributes to an individual menu(3x,n,n tk_menuSetFocus) item. It's
           a pointer to an associative array relating menu(3x,n,n tk_menuSetFocus) values to another
           associative array with the attribute's name as the key and the
           attribute's value as the value.

           To include row and column headings in(1,8) the returned table, you can
           use the -rowheaders and -colheaders parameters.  Both of these
           accept(2,8) a pointer to an array of headings to use.  The headings are
           just decorative.  They don't reorganize the interpretation of the
           checkboxes -- they're still a single named(5,8) unit.

       When the form is processed, all checked boxes will be returned as a
       list under the parameter name 'group_name'.  The values of the "on"
       checkboxes can be retrieved with:

             @turned_on = $query->param('group_name');

       The value returned by checkbox_group() is actually an array of button
       elements.  You can capture them and use them within tables, lists, or
       in(1,8) other creative ways:

           @h = $query->checkbox_group(-name=>'group_name',-values=>\@values);
           &use_in_creative_way(@h);

       JAVASCRIPTING: checkbox_group() recognizes the -onClick parameter.
       This specifies a JavaScript code fragment or function call to be exe-
       cuted every time(1,2,n) the user clicks on any of the buttons in(1,8) the group.
       You can retrieve the identity of the particular button clicked on using
       the "this" variable.

       CREATING A STANDALONE CHECKBOX

           print $query->checkbox(-name=>'checkbox_name',
                                  -checked=>1,
                                  -value=>'ON',
                                  -label=>'CLICK ME');

               -or-

           print $query->checkbox('checkbox_name','checked','ON','CLICK ME');

       checkbox() is used to create an isolated checkbox that isn't logically
       related to any others.

       Parameters:
       1.  The first parameter is the required name for the checkbox (-name).
           It will also be used for the user-readable label printed next to
           the checkbox.

       2.  The optional second parameter (-checked) specifies that the check-
           box is turned on by default.  Synonyms are -selected and -on.

       3.  The optional third parameter (-value) specifies the value of the
           checkbox when it is checked.  If not provided, the word "on" is
           assumed.

       4.  The optional fourth parameter (-label) is the user-readable label
           to be attached to the checkbox.  If not provided, the checkbox name
           is used.

       The value of the checkbox can be retrieved using:

           $turned_on = $query->param('checkbox_name');

       JAVASCRIPTING: checkbox() recognizes the -onClick parameter.  See
       checkbox_group() for further details.

       CREATING A RADIO BUTTON GROUP

          print $query->radio_group(-name=>'group_name',
                                    -values=>['eenie','meenie','minie'],
                                    -default=>'meenie',
                                    -linebreak=>'true',
                  -labels=>\%labels,
                  -attributes=>\%attributes);

               -or-

          print $query->radio_group('group_name',['eenie','meenie','minie'],
                   'meenie','true',\%labels,\%attributes);

          HTML3-COMPATIBLE BROWSERS ONLY:

          print $query->radio_group(-name=>'group_name',
                                    -values=>['eenie','meenie','minie','moe'],
                                    -rows=2,-columns=>2);

       radio_group() creates a set(7,n,1 builtins) of logically-related radio buttons (turning
       one member of the group on turns the others off)

       Parameters:
       1.  The first argument is the name of the group and is required
           (-name).

       2.  The second argument (-values) is the list of values for the radio
           buttons.  The values and the labels that appear on the page are
           identical.  Pass an array reference in(1,8) the second argument, either
           using an anonymous array, as shown, or by referencing a named(5,8) array
           as in(1,8) "\@foo".

       3.  The optional third parameter (-default) is the name of the default
           button to turn on. If not specified, the first item will be the
           default.  You can provide a nonexistent button name, such as "-" to
           start up with no buttons selected.

       4.  The optional fourth parameter (-linebreak) can be set(7,n,1 builtins) to 'true' to
           put line breaks between the buttons, creating a vertical list.

       5.  The optional fifth parameter (-labels) is a pointer to an associa-
           tive array relating the radio button values to user-visible labels
           to be used in(1,8) the display.  If not provided, the values themselves
           are displayed.

       6.  HTML3-compatible browsers (such as Netscape) can take advantage of
           the optional parameters -rows, and -columns.  These parameters
           cause radio_group() to return an HTML3 compatible table containing
           the radio group formatted with the specified number of rows and
           columns.  You can provide just the -columns parameter if(3,n) you wish;
           radio_group will calculate the correct number of rows for you.

       6.  The optional sixth parameter (-attributes) is provided to assign
           any of the common HTML attributes to an individual menu(3x,n,n tk_menuSetFocus) item. It's
           a pointer to an associative array relating menu(3x,n,n tk_menuSetFocus) values to another
           associative array with the attribute's name as the key and the
           attribute's value as the value.

           To include row and column headings in(1,8) the returned table, you can
           use the -rowheader and -colheader parameters.  Both of these accept(2,8)
           a pointer to an array of headings to use.  The headings are just
           decorative.  They don't reorganize the interpretation of the radio
           buttons -- they're still a single named(5,8) unit.

       When the form is processed, the selected radio button can be retrieved
       using:

             $which_radio_button = $query->param('group_name');

       The value returned by radio_group() is actually an array of button ele-
       ments.  You can capture them and use them within tables, lists, or in(1,8)
       other creative ways:

           @h = $query->radio_group(-name=>'group_name',-values=>\@values);
           &use_in_creative_way(@h);

       CREATING A SUBMIT BUTTON

          print $query->submit(-name=>'button_name',
                               -value=>'value');

               -or-

          print $query->submit('button_name','value');

       submit() will create the query submission button.  Every form should
       have one of these.

       Parameters:
       1.  The first argument (-name) is optional.  You can give the button a
           name if(3,n) you have several submission buttons in(1,8) your form and you
           want to distinguish between them.

       2.  The second argument (-value) is also optional.  This gives the but-
           ton a value that will be passed to your script in(1,8) the query string.
           The name will also be used as the user-visible label.

       3.  You can use -label as an alias for -value.  I always get confused
           about which of -name and -value changes the user-visible label on
           the button.

       You can figure out which button was pressed by using different values
       for each one:

            $which_one = $query->param('button_name');

       JAVASCRIPTING: radio_group() recognizes the -onClick parameter.  See
       checkbox_group() for further details.

       CREATING A RESET BUTTON

          print $query->reset(1,7,1 tput)

       reset(1,7,1 tput)() creates the "reset(1,7,1 tput)" button.  Note that it restores the form to
       its value from the last time(1,2,n) the script was called, NOT necessarily to
       the defaults.

       Note that this conflicts with the Perl reset(1,7,1 tput)() built-in.  Use
       CORE::reset() to get the original reset(1,7,1 tput) function.

       CREATING A DEFAULT BUTTON

          print $query->defaults('button_label')

       defaults() creates a button that, when invoked, will cause the form to
       be completely reset(1,7,1 tput) to its defaults, wiping out all the changes the
       user ever made.

       CREATING A HIDDEN FIELD

               print $query->hidden(-name=>'hidden_name',
                                    -default=>['value1','value2'...]);

                       -or-

               print $query->hidden('hidden_name','value1','value2'...);

       hidden() produces a text field that can't be seen by the user.  It is
       useful for passing state variable information from one invocation of
       the script to the next.

       Parameters:
       1.  The first argument is required and specifies the name of this field
           (-name).

       2.  The second argument is also required and specifies its value
           (-default).  In the named(5,8) parameter style of calling, you can pro-
           vide a single value here or a reference to a whole list

       Fetch the value of a hidden field this way:

            $hidden_value = $query->param('hidden_name');

       Note, that just like all the other form elements, the value of a hidden
       field is "sticky".  If you want to replace a hidden field with some
       other values after the script has been called once you'll have to do it
       manually:

            $query->param('hidden_name','new','values','here');

       CREATING A CLICKABLE IMAGE BUTTON

            print $query->image_button(-name=>'button_name',
                                       -src=>'/source/URL',
                                       -align=>'MIDDLE');

               -or-

            print $query->image_button('button_name','/source/URL','MIDDLE');

       image_button() produces a clickable image.  When it's clicked on the
       position of the click is returned to your script as "button_name.x" and
       "button_name.y", where "button_name" is the name you've assigned to it.

       JAVASCRIPTING: image_button() recognizes the -onClick parameter.  See
       checkbox_group() for further details.

       Parameters:
       1.  The first argument (-name) is required and specifies the name of
           this field.

       2.  The second argument (-src) is also required and specifies the URL

       3. The third option (-align, optional) is an alignment type, and may be
       TOP, BOTTOM or MIDDLE

       Fetch the value of the button this way:
            $x = $query->param('button_name.x');
            $y = $query->param('button_name.y');

       CREATING A JAVASCRIPT ACTION BUTTON

            print $query->button(-name=>'button_name',
                                 -value=>'user visible label',
                                 -onClick=>"do_something()");

               -or-

            print $query->button('button_name',"do_something()");

       button() produces a button that is compatible with Netscape 2.0's
       JavaScript.  When it's pressed the fragment of JavaScript code pointed
       to by the -onClick parameter will be executed.  On non-Netscape
       browsers this form element will probably not even display.

HTTP COOKIES
       Netscape browsers versions 1.1 and higher, and all versions of Internet
       Explorer, support a so-called "cookie" designed to help maintain state
       within a browser session.  CGI.pm has several methods that support
       cookies.

       A cookie is a name=value pair much like the named(5,8) parameters in(1,8) a CGI
       query string.  CGI scripts create one or more cookies and send(2,n) them to
       the browser in(1,8) the HTTP header.  The browser maintains a list of cook-
       ies that belong to a particular Web server, and returns them to the CGI
       script during subsequent interactions.

       In addition to the required name=value pair, each cookie has several
       optional attributes:

       1. an expiration time(1,2,n)
           This is a time(1,2,n)/date string(3,n) (in(1,8) a special GMT format) that indicates
           when a cookie expires.  The cookie will be saved and returned to
           your script until this expiration date is reached if(3,n) the user exits
           the browser and restarts it.  If an expiration date isn't speci-
           fied, the cookie will remain active until the user quits the
           browser.

       2. a domain
           This is a partial or complete domain name for which the cookie is
           valid.  The browser will return the cookie to any host(1,5) that matches
           the partial domain name.  For example, if(3,n) you specify a domain name
           of ".capricorn.com", then the browser will return the cookie to Web
           servers running on any of the machines "www.capricorn.com",
           "www2.capricorn.com", "feckless.capricorn.com", etc.  Domain names
           must contain at least two periods to prevent attempts to match on
           top level domains like ".edu".  If no domain is specified, then the
           browser will only return the cookie to servers on the host(1,5) the
           cookie originated from.

       3. a path
           If you provide a cookie path attribute, the browser will check it
           against your script's URL before returning the cookie.  For exam-
           ple, if(3,n) you specify the path "/cgi-bin", then the cookie will be
           returned to each of the scripts "/cgi-bin/tally.pl",
           "/cgi-bin/order.pl", and "/cgi-bin/customer_service/complain.pl",
           but not to the script "/cgi-private/site_admin.pl".  By default,
           path is set(7,n,1 builtins) to "/", which causes the cookie to be sent to any CGI
           script on your site.

       4. a "secure" flag
           If the "secure" attribute is set(7,n,1 builtins), the cookie will only be sent to
           your script if(3,n) the CGI request is occurring on a secure channel,
           such as SSL.

       The interface to HTTP cookies is the cookie() method:

           $cookie = $query->cookie(-name=>'sessionID',
                                    -value=>'xyzzy',
                                    -expires=>'+1h',
                                    -path=>'/cgi-bin/database',
                                    -domain=>'.capricorn.org',
                                    -secure=>1);
           print $query->header(-cookie=>$cookie);

       cookie() creates a new cookie.  Its parameters include:

       -name
           The name of the cookie (required).  This can be any string(3,n) at all.
           Although browsers limit their cookie names to non-whitespace
           alphanumeric characters, CGI.pm removes this restriction by escap-
           ing and unescaping cookies behind the scenes.

       -value
           The value of the cookie.  This can be any scalar value, array ref-
           erence, or even associative array reference.  For example, you can
           store an entire associative array into a cookie this way:

                   $cookie=$query->cookie(-name=>'family information',
                                          -value=>\%childrens_ages);

       -path
           The optional partial path for which this cookie will be valid, as
           described above.

       -domain
           The optional partial domain for which this cookie will be valid, as
           described above.

       -expires
           The optional expiration date for this cookie.  The format is as
           described in(1,8) the section on the header() method:

                   "+1h"  one hour from now

       -secure
           If set(7,n,1 builtins) to true, this cookie will only be used within a secure SSL
           session.

       The cookie created by cookie() must be incorporated into the HTTP
       header within the string(3,n) returned by the header() method:

               print $query->header(-cookie=>$my_cookie);

       To create multiple cookies, give header() an array reference:

               $cookie1 = $query->cookie(-name=>'riddle_name',
                                         -value=>"The Sphynx's Question");
               $cookie2 = $query->cookie(-name=>'answers',
                                         -value=>\%answers);
               print $query->header(-cookie=>[$cookie1,$cookie2]);

       To retrieve a cookie, request it by name by calling cookie() method
       without the -value parameter:

               use CGI;
               $query = new CGI;
               $riddle = $query->cookie('riddle_name');
               %answers = $query->cookie('answers');

       Cookies created with a single scalar value, such as the "riddle_name"
       cookie, will be returned in(1,8) that form.  Cookies with array and hash
       values can also be retrieved.

       The cookie and CGI namespaces are separate.  If you have a parameter
       named(5,8) 'answers' and a cookie named(5,8) 'answers', the values retrieved by
       param() and cookie() are independent of each other.  However, it's sim-
       ple to turn a CGI parameter into a cookie, and vice-versa:

          # turn a CGI parameter into a cookie
          $c=$q->cookie(-name=>'answers',-value=>[$q->param('answers')]);
          # vice-versa
          $q->param(-name=>'answers',-value=>[$q->cookie('answers')]);

       See the cookie.cgi example script for some ideas on how to use cookies
       effectively.

WORKING WITH FRAMES
       It's possible for CGI.pm scripts to write(1,2) into several browser panels
       and windows using the HTML 4 frame mechanism.  There are three tech-
       niques for defining new frames programmatically:

       1. Create a <Frameset> document
           After writing out the HTTP header, instead of creating a standard
           HTML document using the start_html() call, create a <frameset> doc-
           ument that defines the frames on the page.  Specify your script(s)
           (with appropriate parameters) as the SRC for each of the frames.

           There is no specific support for creating <frameset> sections in(1,8)
           CGI.pm, but the HTML is very simple to write.  See the frame docu-
           mentation in(1,8) Netscape's home pages for details

             http://home.netscape.com/assist/net_sites/frames.html

       2. Specify the destination for the document in(1,8) the HTTP header
           You may provide a -target parameter to the header() method:

               print $q->header(-target=>'ResultsWindow');

           This will tell the browser to load(7,n) the output of your script into
           the frame named(5,8) "ResultsWindow".  If a frame of that name doesn't
           already exist, the browser will pop up a new window and load(7,n) your
           script's document into that.  There are a number of magic(4,5) names
           that you can use for targets.  See the frame documents on
           Netscape's home pages for details.

       3. Specify the destination for the document in(1,8) the <form> tag
           You can specify the frame to load(7,n) in(1,8) the FORM tag itself.  With
           CGI.pm it looks like this:

               print $q->start_form(-target=>'ResultsWindow');

           When your script is reinvoked by the form, its output will be
           loaded into the frame named(5,8) "ResultsWindow".  If one doesn't
           already exist a new window will be created.

       The script "frameset.cgi" in(1,8) the examples directory shows one way to
       create pages in(1,8) which the fill-out form and the response live in(1,8) side-
       by-side frames.

LIMITED SUPPORT FOR CASCADING STYLE SHEETS
       CGI.pm has limited support for HTML3's cascading style sheets (css).
       To incorporate a stylesheet into your document, pass the start_html()
       method a -style parameter.  The value of this parameter may be a
       scalar, in(1,8) which case it is treated as the source URL for the
       stylesheet, or it may be a hash reference.  In the latter case you
       should provide the hash with one or more of -src or -code.  -src points
       to a URL where an externally-defined stylesheet can be found.  -code
       points to a scalar value to be incorporated into a <style> section.
       Style definitions in(1,8) -code override similarly-named ones in(1,8) -src, hence
       the name "cascading."

       You may also specify the type of the stylesheet by adding the optional
       -type parameter to the hash pointed to by -style.  If not specified,
       the style defaults to 'text/css'.

       To refer to a style within the body of your document, add the -class
       parameter to any HTML element:

           print h1({-class=>'Fancy'},'Welcome to the Party');

       Or define styles on the fly with the -style parameter:

           print h1({-style=>'Color: red;'},'Welcome to Hell');

       You may also use the new span() element to apply a style to a section
       of text:

           print span({-style=>'Color: red;'},
                      h1('Welcome to Hell'),
                      "Where did that handbasket get to?"
                      );

       Note that you must import the ":html3" definitions to have the span()
       method available.  Here's a quick and dirty example of using CSS's.
       See the CSS specification at http://www.w3.org/pub/WWW/TR/Wd-css-1.html
       for more information.

           use CGI qw/:standard :html3/;

           #here's a stylesheet incorporated directly into the page
           $newStyle=<<END;
           <!--
           P.Tip {
               margin-right: 50pt;
               margin-left: 50pt;
               color: red;
           }
           P.Alert {
               font-size: 30pt;
               font-family: sans-serif;
             color: red;
           }
           -->
           END
           print header();
           print start_html( -title=>'CGI with Style',
                             -style=>{-src=>'http://www.capricorn.com/style/st1.css',
                                      -code=>$newStyle}
                            );
           print h1('CGI with Style'),
                 p({-class=>'Tip'},
                   "Better read(2,n,1 builtins) the cascading style sheet spec before playing with this!"),
                 span({-style=>'color: magenta'},
                      "Look Mom, no hands!",
                      p(),
                      "Whooo wee!"
                      );
           print end_html;

       Pass an array reference to -code or -src in(1,8) order to incorporate multi-
       ple stylesheets into your document.

       Should you wish to incorporate a verbatim stylesheet that includes
       arbitrary formatting in(1,8) the header, you may pass a -verbatim tag to the
       -style hash, as follows:

       print $q->start_html (-STYLE  =>  {-verbatim => '@import
       url("/server-common/css/'.$cssFile.'");',
                             -src      =>  '/server-common/css/core.css'});
       </blockquote></pre>

       This will generate an HTML header that contains this:

        <link(1,2) rel="stylesheet" type="text/css"  href="/server-common/css/core.css">
          <style type="text/css">
          @import url("/server-common/css/main.css");
          </style>

       Any additional arguments passed in(1,8) the -style value will be incorpo-
       rated into the <link(1,2)> tag.  For example:

        start_html(-style=>{-src=>['/styles/print.css','/styles/layout.css'],
                                 -media => 'all'});

       This will give:

        <link(1,2) rel="stylesheet" type="text/css" href="/styles/print.css" media="all"/>
        <link(1,2) rel="stylesheet" type="text/css" href="/styles/layout.css" media="all"/>

       <p>

       To make more complicated <link(1,2)> tags, use the Link() function and pass
       it to start_html() in(1,8) the -head argument, as in:

         @h = (Link({-rel=>'stylesheet',-type=>'text/css',-src=>'/ss/ss.css',-media=>'all'}),
               Link({-rel=>'stylesheet',-type=>'text/css',-src=>'/ss/fred.css',-media=>'paper'}));
         print start_html({-head=>\@h})

DEBUGGING
       If you are running the script from the command line or in(1,8) the perl
       debugger, you can pass the script a list of keywords or parameter=value
       pairs on the command line or from standard input (you don't have to
       worry about tricking your script into reading from environment vari-
       ables).  You can pass keywords like this:

           your_script.pl keyword1 keyword2 keyword3

       or this:

          your_script.pl keyword1+keyword2+keyword3

       or this:

           your_script.pl name1=value1 name2=value2

       or this:

           your_script.pl name1=value1&name2=value2

       To turn off this feature, use the -no_debug pragma.

       To test the POST method, you may enable full debugging with the -debug
       pragma.  This will allow you to feed newline-delimited name=value pairs
       to the script on standard input.

       When debugging, you can use quotes and backslashes to escape characters
       in(1,8) the familiar shell manner, letting you place spaces and other funny
       characters in(1,8) your parameter=value pairs:

          your_script.pl "name1='I am a long value'" "name2=two\ words"

       Finally, you can set(7,n,1 builtins) the path info(1,5,n) for the script by prefixing the
       first name/value parameter with the path followed by a question mark
       (?):

           your_script.pl /your/path/here?name1=value1&name2=value2

       DUMPING OUT ALL THE NAME/VALUE PAIRS

       The Dump() method produces a string(3,n) consisting of all the query's
       name/value pairs formatted nicely as a nested list.  This is useful for
       debugging purposes:

           print $query->Dump

       Produces something that looks like:

           <ul>
           <li>name1
               <ul>
               <li>value1
               <li>value2
               </ul>
           <li>name2
               <ul>
               <li>value1
               </ul>
           </ul>

       As a shortcut, you can interpolate the entire CGI object into a string(3,n)
       and it will be replaced with the a nice(1,2) HTML dump shown above:

           $query=new CGI;
           print "<h2>Current Values</h2> $query\n";

FETCHING ENVIRONMENT VARIABLES
       Some of the more useful environment variables can be fetched through
       this interface.  The methods are as follows:

       Accept()
           Return a list of MIME types that the remote browser accepts. If you
           give this method a single argument corresponding to a MIME type, as
           in(1,8) $query->Accept('text/html'), it will return a floating point
           value corresponding to the browser's preference for this type from
           0.0 (don't want) to 1.0.  Glob types (e.g. text/*) in(1,8) the browser's
           accept(2,8) list are handled correctly.

           Note that the capitalization changed between version(1,3,5) 2.43 and 2.44
           in(1,8) order to avoid conflict with Perl's accept(2,8)() function.

       raw_cookie()
           Returns the HTTP_COOKIE variable, an HTTP extension implemented by
           Netscape browsers version(1,3,5) 1.1 and higher, and all versions of
           Internet Explorer.  Cookies have a special format, and this method
           call just returns the raw(3x,7,8,3x cbreak) form (?cookie dough).  See cookie() for
           ways of setting and retrieving cooked cookies.

           Called with no parameters, raw_cookie() returns the packed cookie
           structure.  You can separate it into individual cookies by split-
           ting on the character sequence "; ".  Called with the name of a
           cookie, retrieves the unescaped form of the cookie.  You can use
           the regular cookie() method to get the names, or use the
           raw_fetch() method from the CGI::Cookie module.

       user_agent()
           Returns the HTTP_USER_AGENT variable.  If you give this method a
           single argument, it will attempt to pattern match on it, allowing
           you to do something like $query->user_agent(netscape);

       path_info()
           Returns additional path information from the script URL.  E.G.
           fetching /cgi-bin/your_script/additional/stuff will result in(1,8)
           $query->path_info() returning "/additional/stuff".

           NOTE: The Microsoft Internet Information Server is broken with
           respect to additional path information.  If you use the Perl DLL
           library, the IIS server will attempt to execute the additional path
           information as a Perl script.  If you use the ordinary file(1,n) associ-
           ations mapping, the path information will be present in(1,8) the envi-
           ronment, but incorrect.  The best thing to do is to avoid using
           additional path information in(1,8) CGI scripts destined for use with
           IIS.

       path_translated()
           As per path_info() but returns the additional path information
           translated into a physical path, e.g.
           "/usr/local/etc/httpd/htdocs/additional/stuff".

           The Microsoft IIS is broken with respect to the translated path as
           well.

       remote_host()
           Returns either the remote host(1,5) name or IP address.  if(3,n) the former
           is unavailable.

       script_name() Return the script name as a partial URL, for self-refer-
       ing scripts.
       referer()
           Return the URL of the page the browser was viewing prior to fetch-
           ing your script.  Not available for all browsers.

       auth_type ()
           Return the authorization/verification method in(1,8) use for this
           script, if(3,n) any.

       server_name ()
           Returns the name of the server, usually the machine's host(1,5) name.

       virtual_host ()
           When using virtual(5,8) hosts, returns the name of the host(1,5) that the
           browser attempted to contact

       server_port ()
           Return the port that the server is listening on.

       virtual_port ()
           Like server_port() except that it takes virtual(5,8) hosts into account.
           Use this when running with virtual(5,8) hosts.

       server_software ()
           Returns the server software and version(1,3,5) number.

       remote_user ()
           Return the authorization/verification name used for user verifica-
           tion, if(3,n) this script is protected.

       user_name ()
           Attempt to obtain the remote user's name, using a variety of dif-
           ferent techniques.  This only works with older browsers such as
           Mosaic.  Newer browsers do not report the user name for privacy
           reasons!

       request_method()
           Returns the method used to access(2,5) your script, usually one of
           'POST', 'GET' or 'HEAD'.

       content_type()
           Returns the content_type of data submitted in(1,8) a POST, generally
           multipart/form-data or application/x-www-form-urlencoded

       http()
           Called with no arguments returns the list of HTTP environment vari-
           ables, including such things as HTTP_USER_AGENT, HTTP_ACCEPT_LAN-
           GUAGE, and HTTP_ACCEPT_CHARSET, corresponding to the like-named
           HTTP header fields in(1,8) the request.  Called with the name of an HTTP
           header field, returns its value.  Capitalization and the use of
           hyphens versus underscores are not significant.

           For example, all three of these examples are equivalent:

              $requested_language = $q->http('Accept-language');
              $requested_language = $q->http('Accept_language');
              $requested_language = $q->http('HTTP_ACCEPT_LANGUAGE');

       https()
           The same as http(), but operates on the HTTPS environment variables
           present when the SSL protocol is in(1,8) effect.  Can be used to deter-
           mine whether SSL is turned on.

USING NPH SCRIPTS
       NPH, or "no-parsed-header", scripts bypass the server completely by
       sending the complete HTTP header directly to the browser.  This has
       slight performance benefits, but is of most use for taking advantage of
       HTTP extensions that are not directly supported by your server, such as
       server push and PICS headers.

       Servers use a variety of conventions for designating CGI scripts as
       NPH.  Many Unix servers look(1,8,3 Search::Dict) at the beginning of the script's name for
       the prefix "nph-".  The Macintosh WebSTAR server and Microsoft's Inter-
       net Information Server, in(1,8) contrast, try to decide whether a program is
       an NPH script by examining the first line of script output.

       CGI.pm supports NPH scripts with a special NPH mode.  When in(1,8) this
       mode, CGI.pm will output the necessary extra header information when
       the header() and redirect() methods are called.

       The Microsoft Internet Information Server requires NPH mode.  As of
       version(1,3,5) 2.30, CGI.pm will automatically detect when the script is run-
       ning under IIS and put itself into this mode.  You do not need to do
       this manually, although it won't hurt anything if(3,n) you do.  However,
       note that if(3,n) you have applied Service Pack 6, much of the functionality
       of NPH scripts, including the ability to redirect while setting a
       cookie, b<do not work at all> on IIS without a special patch from
       Microsoft.  See http://support.microsoft.com/support/kb/arti-
       cles/Q280/3/41.ASP: Non-Parsed Headers Stripped From CGI Applications
       That Have nph- Prefix in(1,8) Name.

       In the use statement
           Simply add the "-nph" pragmato the list of symbols to be imported
           into your script:

                 use CGI qw(:standard -nph)

       By calling the nph() method:
           Call nph() with a non-zero parameter at any point after using
           CGI.pm in(1,8) your program.

                 CGI->nph(1)

       By using -nph parameters
           in(1,8) the header() and redirect()  statements:

                 print $q->header(-nph=>1);

Server Push
       CGI.pm provides four simple functions for producing multipart documents
       of the type needed to implement server push.  These functions were gra-
       ciously provided by Ed Jordan <ed@fidalgo.net>.  To import these into
       your namespace, you must import the ":push" set.  You are also advised
       to put the script into NPH mode and to set(7,n,1 builtins) $| to 1 to avoid buffering
       problems.

       Here is a simple script that demonstrates server push:

         #!/usr/local/bin/perl
         use CGI qw/:push -nph/;
         $| = 1;
         print multipart_init(-boundary=>'----here we go!');
         foreach (0 .. 4) {
             print multipart_start(-type=>'text/plain'),
                   "The current time(1,2,n) is ",scalar(localtime),"\n";
             if(3,n) ($_ < 4) {
                     print multipart_end;
             } else {
                     print multipart_final;
             }
             sleep(1,3) 1;
         }

       This script initializes server push by calling multipart_init().  It
       then enters a loop in(1,8) which it begins a new multipart section by call-
       ing multipart_start(), prints the current local time(1,2,n), and ends a multi-
       part section with multipart_end().  It then sleeps a second, and begins
       again. On the final iteration, it ends the multipart section with mul-
       tipart_final() rather than with multipart_end().

       multipart_init()
             multipart_init(-boundary=>$boundary);

           Initialize the multipart system.  The -boundary argument specifies
           what MIME boundary string(3,n) to use to separate parts of the document.
           If not provided, CGI.pm chooses a reasonable boundary for you.

       multipart_start()
             multipart_start(-type=>$type)

           Start a new part of the multipart document using the specified MIME
           type.  If not specified, text/html is assumed.

       multipart_end()
             multipart_end()

           End a part.  You must remember to call multipart_end() once for
           each multipart_start(), except at the end of the last part of the
           multipart document when multipart_final() should be called instead
           of multipart_end().

       multipart_final()
             multipart_final()

           End all parts.  You should call multipart_final() rather than mul-
           tipart_end() at the end of the last part of the multipart document.

       Users interested in(1,8) server push applications should also have a look(1,8,3 Search::Dict) at
       the CGI::Push module.

       Only Netscape Navigator supports server push.  Internet Explorer
       browsers do not.

Avoiding Denial of Service Attacks
       A potential problem with CGI.pm is that, by default, it attempts to
       process form POSTings no matter how large they are.  A wily hacker
       could attack your site by sending a CGI script a huge POST of many
       megabytes.  CGI.pm will attempt to read(2,n,1 builtins) the entire POST into a vari-
       able, growing hugely in(1,8) size until it runs out of memory.  While the
       script attempts to allocate the memory the system may slow down dramat-
       ically.  This is a form of denial of service attack.

       Another possible attack is for the remote user to force CGI.pm to
       accept(2,8) a huge file(1,n) upload.  CGI.pm will accept(2,8) the upload and store it
       in(1,8) a temporary directory even if(3,n) your script doesn't expect to receive
       an uploaded file.  CGI.pm will delete the file(1,n) automatically when it
       terminates, but in(1,8) the meantime the remote user may have filled up the
       server's disk space, causing problems for other programs.

       The best way to avoid denial of service attacks is to limit the amount
       of memory, CPU time(1,2,n) and disk space that CGI scripts can use.  Some Web
       servers come with built-in facilities to accomplish this. In other
       cases, you can use the shell limit or ulimit commands to put ceilings
       on CGI resource usage.

       CGI.pm also has some simple built-in protections against denial of ser-
       vice attacks, but you must activate them before you can use them.
       These take the form of two global variables in(1,8) the CGI name space:

       $CGI::POST_MAX
           If set(7,n,1 builtins) to a non-negative integer, this variable puts(3,n) a ceiling on
           the size of POSTings, in(1,8) bytes.  If CGI.pm detects a POST that is
           greater than the ceiling, it will immediately exit(3,n,1 builtins) with an error(8,n)
           message.  This value will affect both ordinary POSTs and multipart
           POSTs, meaning that it limits the maximum size of file(1,n) uploads as
           well.  You should set(7,n,1 builtins) this to a reasonably high value, such as 1
           megabyte.

       $CGI::DISABLE_UPLOADS
           If set(7,n,1 builtins) to a non-zero value, this will disable file(1,n) uploads com-
           pletely.  Other fill-out form values will work as usual.

       You can use these variables in(1,8) either of two ways.

       1. On a script-by-script basis
           Set the variable at the top of the script, right after the "use"
           statement:

               use CGI qw/:standard/;
               use CGI::Carp 'fatalsToBrowser';
               $CGI::POST_MAX=1024 * 100;  # max 100K posts
               $CGI::DISABLE_UPLOADS = 1;  # no uploads

       2. Globally for all scripts
           Open up CGI.pm, find the definitions for $POST_MAX and $DIS-
           ABLE_UPLOADS, and set(7,n,1 builtins) them to the desired values.  You'll find them
           towards the top of the file(1,n) in(1,8) a subroutine named(5,8) initialize_glob-
           als().

       An attempt to send(2,n) a POST larger than $POST_MAX bytes will cause
       param() to return an empty CGI parameter list.  You can test for this
       event by checking cgi_error(), either after you create the CGI object
       or, if(3,n) you are using the function-oriented interface, call <param()>
       for the first time.  If the POST was intercepted, then cgi_error() will
       return the message "413 POST too large".

       This error(8,n) message is actually defined by the HTTP protocol, and is
       designed to be returned to the browser as the CGI script's status
        code.  For example:

          $uploaded_file = param('upload');
          if(3,n) (!$uploaded_file && cgi_error()) {
             print header(-status=>cgi_error());
             exit(3,n,1 builtins) 0;
          }

       However it isn't clear(1,3x,3x clrtobot) that any browser currently knows what to do with
       this status code.  It might be better just to create an HTML page that
       warns the user of the problem.

COMPATIBILITY WITH CGI-LIB.PL
       To make it easier to port existing programs that use cgi-lib.pl the
       compatibility routine "ReadParse" is provided.  Porting is simple:

       OLD VERSION
           require "cgi-lib.pl";
           &ReadParse;
           print "The value of the antique is $in(1,8){antique}.\n";

       NEW VERSION
           use CGI;
           CGI::ReadParse;
           print "The value of the antique is $in(1,8){antique}.\n";

       CGI.pm's ReadParse() routine creates a tied variable named(5,8) %in(1,8), which
       can be accessed to obtain the query variables.  Like ReadParse, you can
       also provide your own variable.  Infrequently used features of Read-
       Parse, such as the creation of @in(1,8) and $in(1,8) variables, are not sup-
       ported.

       Once you use ReadParse, you can retrieve the query object itself this
       way:

           $q = $in(1,8){CGI};
           print $q->textfield(-name=>'wow',
                               -value=>'does this really work?');

       This allows you to start using the more interesting features of CGI.pm
       without rewriting your old scripts from scratch.

AUTHOR INFORMATION
       Copyright 1995-1998, Lincoln D. Stein.  All rights reserved.

       This library is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

       Address bug reports and comments to: lstein@cshl.org.  When sending bug
       reports, please provide the version(1,3,5) of CGI.pm, the version(1,3,5) of Perl, the
       name and version(1,3,5) of your Web server, and the name and version(1,3,5) of the
       operating system you are using.  If the problem is even remotely
       browser dependent, please provide information about the affected brow-
       ers as well.

CREDITS
       Thanks very much to:

       Matt Heffron (heffron@falstaff.css.beckman.com)
       James Taylor (james.taylor@srs.gov)
       Scott Anguish <sanguish@digifix.com>
       Mike Jewell (mlj3u@virginia.edu)
       Timothy Shimmin (tes@kbs.citri.edu.au)
       Joergen Haegg (jh@axis.se)
       Laurent Delfosse (delfosse@delfosse.com)
       Richard Resnick (applepi1@aol.com)
       Craig Bishop (csb@barwonwater.vic.gov.au)
       Tony Curtis (tc@vcpc.univie.ac.at)
       Tim Bunce (Tim.Bunce@ig.co.uk)
       Tom Christiansen (tchrist@convex.com)
       Andreas Koenig (k@franz.ww.TU-Berlin.DE)
       Tim MacKenzie (Tim.MacKenzie@fulcrum.com.au)
       Kevin B. Hendricks (kbhend@dogwood.tyler.wm.edu)
       Stephen Dahmen (joyfire@inxpress.net)
       Ed Jordan (ed@fidalgo.net)
       David Alan Pisoni (david@cnation.com)
       Doug MacEachern (dougm@opengroup.org)
       Robin Houston (robin@oneworld.org)
       ...and many many more...
           for suggestions and bug fixes.

A COMPLETE EXAMPLE OF A SIMPLE FORM-BASED SCRIPT
               #!/usr/local/bin/perl

               use CGI;

               $query = new CGI;

               print $query->header;
               print $query->start_html("Example CGI.pm Form");
               print "<h1> Example CGI.pm Form</h1>\n";
               &print_prompt($query);
               &do_work($query);
               &print_tail;
               print $query->end_html;

               sub print_prompt {
                  my($query) = @_;

                  print $query->start_form;
                  print "<em>What's your name?</em><br>";
                  print $query->textfield('name');
                  print $query->checkbox('Not my real name');

                  print "<p><em>Where can you find English Sparrows?</em><br>";
                  print $query->checkbox_group(
                                        -name=>'Sparrow locations',
                                        -values=>[England,France,Spain,Asia,Hoboken],
                                        -linebreak=>'yes',
                                        -defaults=>[England,Asia]);

                  print "<p><em>How far can they fly?</em><br>",
                       $query->radio_group(
                               -name=>'how far',
                               -values=>['10 ft','1 mile','10 miles','real far'],
                               -default=>'1 mile');

                  print "<p><em>What's your favorite color?</em>  ";
                  print $query->popup_menu(-name=>'Color',
                                           -values=>['black','brown','red','yellow'],
                                           -default=>'red');

                  print $query->hidden('Reference','Monty Python and the Holy Grail');

                  print "<p><em>What have you got there?</em><br>";
                  print $query->scrolling_list(
                                -name=>'possessions',
                                -values=>['A Coconut','A Grail','An Icon',
                                          'A Sword','A Ticket'],
                                -size=>5,
                                -multiple=>'true');

                  print "<p><em>Any parting comments?</em><br>";
                  print $query->textarea(-name=>'Comments',
                                         -rows=>10,
                                         -columns=>50);

                  print "<p>",$query->reset(1,7,1 tput);
                  print $query->submit('Action','Shout');
                  print $query->submit('Action','Scream');
                  print $query->endform;
                  print "<hr>\n";
               }

               sub do_work {
                  my($query) = @_;
                  my(@values,$key);

                  print "<h2>Here are the current settings in(1,8) this form</h2>";

                  foreach $key ($query->param) {
                     print "<strong>$key</strong> -> ";
                     @values = $query->param($key);
                     print join(1,n)(", ",@values),"<br>\n";
                 }
               }

               sub print_tail {
                  print <<END;
               <hr>
               <address>Lincoln D. Stein</address><br>
               <a href="/">Home Page</a>
               END
               }

BUGS
       Please report them.

SEE ALSO
       CGI::Carp, CGI::Fast, CGI::Pretty



perl v5.8.5                       2001-09-21                            CGI(3)

References for this manual (incoming links)