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perlreref(1) - perlreref - Perl Regular Expressions Reference - man 1 perlreref

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PERLREREF(1)           Perl Programmers Reference Guide           PERLREREF(1)

       perlreref - Perl Regular Expressions Reference

       This is a quick reference to Perl's regular expressions.  For full
       information see perlre and perlop, as well as the "SEE ALSO" section in(1,8)
       this document.


         =~ determines to which variable the regex(3,7) is applied.
            In its absence, $_ is used.

               $var =~ /foo/;

         !~ determines to which variable the regex(3,7) is applied,
            and negates the result of the match; it returns
            false if(3,n) the match succeeds, and true if(3,n) it fails.

              $var !~ /foo/;

         m/pattern/igmsoxc searches a string(3,n) for a pattern match,
            applying the given options.

               i  case-Insensitive
               g  Global - all occurrences
               m  Multiline mode - ^ and $ match internal lines
               s  match as a Single line - . matches \n
               o  compile pattern Once
               x  eXtended legibility - free whitespace and comments
               c  don't reset(1,7,1 tput) pos on failed matches when using /g

            If 'pattern' is an empty string(3,n), the last I<successfully> matched
            regex(3,7) is used. Delimiters other than '/' may be used for both this
            operator and the following ones.

         qr/pattern/imsox lets you store a regex(3,7) in(1,8) a variable,
            or pass one around. Modifiers as for m// and are stored
            within the regex.

         s/pattern/replacement/igmsoxe substitutes matches of
            'pattern' with 'replacement'. Modifiers as for m//
            with one addition:

               e  Evaluate replacement as an expression

            'e' may be specified multiple times. 'replacement' is interpreted
            as a double quoted string(3,n) unless a single-quote (') is the delimiter.

         ?pattern? is like m/pattern/ but matches only once. No alternate
             delimiters can be used. Must be reset(1,7,1 tput) with L<reset(1,7,1 tput)|perlfunc/reset(1,7,1 tput)>.


          \       Escapes the character immediately following it
          .       Matches any single character except a newline (unless /s is used)
          ^       Matches at the beginning of the string(3,n) (or line, if(3,n) /m is used)
          $       Matches at the end of the string(3,n) (or line, if(3,n) /m is used)
          *       Matches the preceding element 0 or more times
          +       Matches the preceding element 1 or more times
          ?       Matches the preceding element 0 or 1 times
          {...}   Specifies a range of occurrences for the element preceding it
          [...]   Matches any one of the characters contained within the brackets
          (...)   Groups subexpressions for capturing to $1, $2...
          (?:...) Groups subexpressions without capturing (cluster)
          |       Matches either the subexpression preceding or following it
          \1, \2 ...  The text from the Nth group


       These work as in(1,8) normal strings.

          \a       Alarm (beep(1,3x,3x curs_beep))
          \e       Escape
          \f       Formfeed
          \n       Newline
          \r       Carriage return
          \t       Tab
          \038     Any octal ASCII value
          \x7f     Any hexadecimal ASCII value
          \x{263a} A wide hexadecimal value
          \cx      Control-x
          \N{name} A named(5,8) character

          \l  Lowercase next character
          \u  Titlecase next character
          \L  Lowercase until \E
          \U  Uppercase until \E
          \Q  Disable pattern metacharacters until \E
          \E  End case modification

       For Titlecase, see "Titlecase".

       This one works differently from normal strings:

          \b  An assertion, not backspace, except in(1,8) a character class


          [amy]    Match 'a', 'm' or 'y'
          [f-j]    Dash specifies "range"
          [f-j-]   Dash escaped or at start or end means 'dash'
          [^f-j]   Caret indicates "match any character _except_ these"

       The following sequences work within or without a character class.  The
       first six are locale(3,5,7) aware, all are Unicode aware.  The default charac-
       ter class equivalent are given.  See perllocale and perlunicode for

          \d      A digit                     [0-9]
          \D      A nondigit                  [^0-9]
          \w      A word character            [a-zA-Z0-9_]
          \W      A non-word character        [^a-zA-Z0-9_]
          \s      A whitespace character      [ \t\n\r\f]
          \S      A non-whitespace character  [^ \t\n\r\f]

          \C      Match a byte (with Unicode, '.' matches a character)
          \pP     Match P-named (Unicode) property
          \p{...} Match Unicode property with long name
          \PP     Match non-P
          \P{...} Match lack of Unicode property with long name
          \X      Match extended unicode sequence

       POSIX character classes and their Unicode and Perl equivalents:

          alnum   IsAlnum              Alphanumeric
          alpha   IsAlpha              Alphabetic
          ascii(1,7)   IsASCII              Any ASCII char
          blank   IsSpace  [ \t]       Horizontal whitespace (GNU extension)
          cntrl   IsCntrl              Control characters
          digit   IsDigit  \d          Digits
          graph   IsGraph              Alphanumeric and punctuation
          lower   IsLower              Lowercase chars (locale(3,5,7) and Unicode aware)
          print   IsPrint              Alphanumeric, punct, and space
          punct   IsPunct              Punctuation
          space   IsSpace  [\s\ck]     Whitespace
                  IsSpacePerl   \s     Perl's whitespace definition
          upper   IsUpper              Uppercase chars (locale(3,5,7) and Unicode aware)
          word    IsWord   \w          Alphanumeric plus _ (Perl extension)
          xdigit  IsXDigit [0-9A-Fa-f] Hexadecimal digit

       Within a character class:

           POSIX       traditional   Unicode
           [:digit:]       \d        \p{IsDigit}
           [:^digit:]      \D        \P{IsDigit}


       All are zero-width assertions.

          ^  Match string(3,n) start (or line, if(3,n) /m is used)
          $  Match string(3,n) end (or line, if(3,n) /m is used) or before newline
          \b Match word boundary (between \w and \W)
          \B Match except at word boundary (between \w and \w or \W and \W)
          \A Match string(3,n) start (regardless of /m)
          \Z Match string(3,n) end (before optional newline)
          \z Match absolute string(3,n) end
          \G Match where previous m//g left off


       Quantifiers are greedy by default -- match the longest leftmost.

          Maximal Minimal Allowed range
          ------- ------- -------------
          {n,m}   {n,m}?  Must occur at least n times but no more than m times
          {n,}    {n,}?   Must occur at least n times
          {n}     {n}?    Must occur exactly n times
          *       *?      0 or more times (same as {0,})
          +       +?      1 or more times (same as {1,})
          ?       ??      0 or 1 time(1,2,n) (same as {0,1})

       There is no quantifier {,n} -- that gets(3,n) understood as a literal


          (?#text)         A comment
          (?imxs-imsx:...) Enable/disable option (as per m// modifiers)
          (?=...)          Zero-width positive lookahead assertion
          (?!...)          Zero-width negative lookahead assertion
          (?<=...)         Zero-width positive lookbehind assertion
          (?<!...)         Zero-width negative lookbehind assertion
          (?>...)          Grab what we can, prohibit backtracking
          (?{ code })      Embedded code, return value becomes $^R
          (??{ code })     Dynamic regex(3,7), return value used as regex(3,7)
          (?(cond)yes|no)  cond being integer corresponding to capturing parens
          (?(cond)yes)        or a lookaround/eval zero-width assertion


          $_    Default variable for operators to use
          $*    Enable multiline matching (deprecated; not in(1,8) 5.9.0 or later)

          $&    Entire matched string(3,n)
          $`    Everything prior to matched string(3,n)
          $'    Everything after to matched string(3,n)

       The use of those last three will slow down all regex(3,7) use within your
       program. Consult perlvar for @LAST_MATCH_START to see equivalent
       expressions that won't cause slow down.  See also Devel::SawAmpersand.

          $1, $2 ...  hold the Xth captured expr(1,3,n)
          $+    Last parenthesized pattern match
          $^N   Holds the most recently closed capture
          $^R   Holds the result of the last (?{...}) expr(1,3,n)
          @-    Offsets of starts of groups. $-[0] holds start of whole match
          @+    Offsets of ends of groups. $+[0] holds end of whole match

       Captured groups are numbered according to their opening paren.


          lc          Lowercase a string(3,n)
          lcfirst     Lowercase first char of a string(3,n)
          uc          Uppercase a string(3,n)
          ucfirst     Titlecase first char of a string(3,n)

          pos         Return or set(7,n,1 builtins) current match position
          quotemeta   Quote metacharacters
          reset(1,7,1 tput)       Reset ?pattern? status
          study       Analyze string(3,n) for optimizing matching

          split(1,n)       Use regex(3,7) to split(1,n) a string(3,n) into parts

       The first four of these are like the escape sequences "\L", "\l", "\U",
       and "\u".  For Titlecase, see "Titlecase".



       Unicode concept which most often is equal to uppercase, but for certain
       characters like the German "sharp s" there is a difference.

       Iain Truskett.

       This document may be distributed under the same terms as Perl itself.

          perlretut for a tutorial on regular expressions.

          perlrequick for a rapid tutorial.

          perlre for more details.

          perlvar for details on the variables.

          perlop for details on the operators.

          perlfunc for details on the functions.

          perlfaq6 for FAQs on regular expressions.

          The re module to alter behaviour and aid debugging.

          "Debugging regular expressions" in(1,8) perldebug

          perluniintro, perlunicode, charnames and locale(3,5,7) for details on
           regexes and internationalisation.

          Mastering Regular Expressions by Jeffrey Friedl
           ( for a thorough grounding and reference on the

       David P.C. Wollmann, Richard Soderberg, Sean M. Burke, Tom Chris-
       tiansen, Jim Cromie, and Jeffrey Goff for useful advice.

perl v5.8.5                       2004-04-23                      PERLREREF(1)

References for this manual (incoming links)