File: //usr/local/ssl/local/share/man/man1/perlreref.1
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.\" ========================================================================
.\"
.IX Title "PERLREREF 1"
.TH PERLREREF 1 "2006-01-07" "perl v5.8.8" "Perl Programmers Reference Guide"
.SH "NAME"
perlreref \- Perl Regular Expressions Reference
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This is a quick reference to Perl's regular expressions.
For full information see perlre and perlop, as well
as the \*(L"\s-1SEE\s0 \s-1ALSO\s0\*(R" section in this document.
.Sh "\s-1OPERATORS\s0"
.IX Subsection "OPERATORS"
.Vb 2
\& =~ determines to which variable the regex is applied.
\& In its absence, $_ is used.
.Ve
.PP
.Vb 1
\& $var =~ /foo/;
.Ve
.PP
.Vb 3
\& !~ determines to which variable the regex is applied,
\& and negates the result of the match; it returns
\& false if the match succeeds, and true if it fails.
.Ve
.PP
.Vb 1
\& $var !~ /foo/;
.Ve
.PP
.Vb 2
\& m/pattern/igmsoxc searches a string for a pattern match,
\& applying the given options.
.Ve
.PP
.Vb 7
\& i case-Insensitive
\& g Global - all occurrences
\& m Multiline mode - ^ and $ match internal lines
\& s match as a Single line - . matches \en
\& o compile pattern Once
\& x eXtended legibility - free whitespace and comments
\& c don't reset pos on failed matches when using /g
.Ve
.PP
.Vb 3
\& If 'pattern' is an empty string, the last I<successfully> matched
\& regex is used. Delimiters other than '/' may be used for both this
\& operator and the following ones.
.Ve
.PP
.Vb 3
\& qr/pattern/imsox lets you store a regex in a variable,
\& or pass one around. Modifiers as for m// and are stored
\& within the regex.
.Ve
.PP
.Vb 3
\& s/pattern/replacement/igmsoxe substitutes matches of
\& 'pattern' with 'replacement'. Modifiers as for m//
\& with one addition:
.Ve
.PP
.Vb 1
\& e Evaluate replacement as an expression
.Ve
.PP
.Vb 2
\& 'e' may be specified multiple times. 'replacement' is interpreted
\& as a double quoted string unless a single-quote (') is the delimiter.
.Ve
.PP
.Vb 2
\& ?pattern? is like m/pattern/ but matches only once. No alternate
\& delimiters can be used. Must be reset with L<reset|perlfunc/reset>.
.Ve
.Sh "\s-1SYNTAX\s0"
.IX Subsection "SYNTAX"
.Vb 13
\& \e Escapes the character immediately following it
\& . Matches any single character except a newline (unless /s is used)
\& ^ Matches at the beginning of the string (or line, if /m is used)
\& $ Matches at the end of the string (or line, if /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
\& \e1, \e2 ... The text from the Nth group
.Ve
.Sh "\s-1ESCAPE\s0 \s-1SEQUENCES\s0"
.IX Subsection "ESCAPE SEQUENCES"
These work as in normal strings.
.PP
.Vb 11
\& \ea Alarm (beep)
\& \ee Escape
\& \ef Formfeed
\& \en Newline
\& \er Carriage return
\& \et Tab
\& \e037 Any octal ASCII value
\& \ex7f Any hexadecimal ASCII value
\& \ex{263a} A wide hexadecimal value
\& \ecx Control-x
\& \eN{name} A named character
.Ve
.PP
.Vb 6
\& \el Lowercase next character
\& \eu Titlecase next character
\& \eL Lowercase until \eE
\& \eU Uppercase until \eE
\& \eQ Disable pattern metacharacters until \eE
\& \eE End case modification
.Ve
.PP
For Titlecase, see \*(L"Titlecase\*(R".
.PP
This one works differently from normal strings:
.PP
.Vb 1
\& \eb An assertion, not backspace, except in a character class
.Ve
.Sh "\s-1CHARACTER\s0 \s-1CLASSES\s0"
.IX Subsection "CHARACTER CLASSES"
.Vb 4
\& [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"
.Ve
.PP
The following sequences work within or without a character class.
The first six are locale aware, all are Unicode aware. The default
character class equivalent are given. See perllocale and
perlunicode for details.
.PP
.Vb 6
\& \ed A digit [0-9]
\& \eD A nondigit [^0-9]
\& \ew A word character [a-zA-Z0-9_]
\& \eW A non-word character [^a-zA-Z0-9_]
\& \es A whitespace character [ \et\en\er\ef]
\& \eS A non-whitespace character [^ \et\en\er\ef]
.Ve
.PP
.Vb 6
\& \eC Match a byte (with Unicode, '.' matches a character)
\& \epP Match P-named (Unicode) property
\& \ep{...} Match Unicode property with long name
\& \ePP Match non-P
\& \eP{...} Match lack of Unicode property with long name
\& \eX Match extended unicode sequence
.Ve
.PP
\&\s-1POSIX\s0 character classes and their Unicode and Perl equivalents:
.PP
.Vb 15
\& alnum IsAlnum Alphanumeric
\& alpha IsAlpha Alphabetic
\& ascii IsASCII Any ASCII char
\& blank IsSpace [ \et] Horizontal whitespace (GNU extension)
\& cntrl IsCntrl Control characters
\& digit IsDigit \ed Digits
\& graph IsGraph Alphanumeric and punctuation
\& lower IsLower Lowercase chars (locale and Unicode aware)
\& print IsPrint Alphanumeric, punct, and space
\& punct IsPunct Punctuation
\& space IsSpace [\es\eck] Whitespace
\& IsSpacePerl \es Perl's whitespace definition
\& upper IsUpper Uppercase chars (locale and Unicode aware)
\& word IsWord \ew Alphanumeric plus _ (Perl extension)
\& xdigit IsXDigit [0-9A-Fa-f] Hexadecimal digit
.Ve
.PP
Within a character class:
.PP
.Vb 3
\& POSIX traditional Unicode
\& [:digit:] \ed \ep{IsDigit}
\& [:^digit:] \eD \eP{IsDigit}
.Ve
.Sh "\s-1ANCHORS\s0"
.IX Subsection "ANCHORS"
All are zero-width assertions.
.PP
.Vb 8
\& ^ Match string start (or line, if /m is used)
\& $ Match string end (or line, if /m is used) or before newline
\& \eb Match word boundary (between \ew and \eW)
\& \eB Match except at word boundary (between \ew and \ew or \eW and \eW)
\& \eA Match string start (regardless of /m)
\& \eZ Match string end (before optional newline)
\& \ez Match absolute string end
\& \eG Match where previous m//g left off
.Ve
.Sh "\s-1QUANTIFIERS\s0"
.IX Subsection "QUANTIFIERS"
Quantifiers are greedy by default \*(-- match the \fBlongest\fR leftmost.
.PP
.Vb 8
\& 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 (same as {0,1})
.Ve
.PP
There is no quantifier {,n} \*(-- that gets understood as a literal string.
.Sh "\s-1EXTENDED\s0 \s-1CONSTRUCTS\s0"
.IX Subsection "EXTENDED CONSTRUCTS"
.Vb 11
\& (?#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, return value used as regex
\& (?(cond)yes|no) cond being integer corresponding to capturing parens
\& (?(cond)yes) or a lookaround/eval zero-width assertion
.Ve
.Sh "\s-1VARIABLES\s0"
.IX Subsection "VARIABLES"
.Vb 2
\& $_ Default variable for operators to use
\& $* Enable multiline matching (deprecated; not in 5.9.0 or later)
.Ve
.PP
.Vb 3
\& $& Entire matched string
\& $` Everything prior to matched string
\& $' Everything after to matched string
.Ve
.PP
The use of those last three will slow down \fBall\fR regex use
within your program. Consult perlvar for \f(CW@LAST_MATCH_START\fR
to see equivalent expressions that won't cause slow down.
See also Devel::SawAmpersand.
.PP
.Vb 6
\& $1, $2 ... hold the Xth captured expr
\& $+ Last parenthesized pattern match
\& $^N Holds the most recently closed capture
\& $^R Holds the result of the last (?{...}) expr
\& @- Offsets of starts of groups. $-[0] holds start of whole match
\& @+ Offsets of ends of groups. $+[0] holds end of whole match
.Ve
.PP
Captured groups are numbered according to their \fIopening\fR paren.
.Sh "\s-1FUNCTIONS\s0"
.IX Subsection "FUNCTIONS"
.Vb 4
\& lc Lowercase a string
\& lcfirst Lowercase first char of a string
\& uc Uppercase a string
\& ucfirst Titlecase first char of a string
.Ve
.PP
.Vb 4
\& pos Return or set current match position
\& quotemeta Quote metacharacters
\& reset Reset ?pattern? status
\& study Analyze string for optimizing matching
.Ve
.PP
.Vb 1
\& split Use regex to split a string into parts
.Ve
.PP
The first four of these are like the escape sequences \f(CW\*(C`\eL\*(C'\fR, \f(CW\*(C`\el\*(C'\fR,
\&\f(CW\*(C`\eU\*(C'\fR, and \f(CW\*(C`\eu\*(C'\fR. For Titlecase, see \*(L"Titlecase\*(R".
.Sh "\s-1TERMINOLOGY\s0"
.IX Subsection "TERMINOLOGY"
\fITitlecase\fR
.IX Subsection "Titlecase"
.PP
Unicode concept which most often is equal to uppercase, but for
certain characters like the German \*(L"sharp s\*(R" there is a difference.
.SH "AUTHOR"
.IX Header "AUTHOR"
Iain Truskett.
.PP
This document may be distributed under the same terms as Perl itself.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.IP "\(bu" 4
perlretut for a tutorial on regular expressions.
.IP "\(bu" 4
perlrequick for a rapid tutorial.
.IP "\(bu" 4
perlre for more details.
.IP "\(bu" 4
perlvar for details on the variables.
.IP "\(bu" 4
perlop for details on the operators.
.IP "\(bu" 4
perlfunc for details on the functions.
.IP "\(bu" 4
perlfaq6 for FAQs on regular expressions.
.IP "\(bu" 4
The re module to alter behaviour and aid
debugging.
.IP "\(bu" 4
\&\*(L"Debugging regular expressions\*(R" in perldebug
.IP "\(bu" 4
perluniintro, perlunicode, charnames and locale
for details on regexes and internationalisation.
.IP "\(bu" 4
\&\fIMastering Regular Expressions\fR by Jeffrey Friedl
(\fIhttp://regex.info/\fR) for a thorough grounding and
reference on the topic.
.SH "THANKS"
.IX Header "THANKS"
David P.C. Wollmann,
Richard Soderberg,
Sean M. Burke,
Tom Christiansen,
Jim Cromie,
and
Jeffrey Goff
for useful advice.