.\" Automatically generated by Pod::Man 4.10 (Pod::Simple 3.35) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. Capital omega is used to do unbreakable dashes and .\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff, .\" nothing in troff, for use with C<>. .tr \(*W- .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' .ie n \{\ . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} .el\{\ . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\} .\" .\" Escape single quotes in literal strings from groff's Unicode transform. .ie \n(.g .ds Aq \(aq .el .ds Aq ' .\" .\" If the F register is >0, we'll generate index entries on stderr for .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index .\" entries marked with X<> in POD. Of course, you'll have to process the .\" output yourself in some meaningful fashion. .\" .\" Avoid warning from groff about undefined register 'F'. .de IX .. .nr rF 0 .if \n(.g .if rF .nr rF 1 .if (\n(rF:(\n(.g==0)) \{\ . if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{\ . nr % 0 . nr F 2 . \} . \} .\} .rr rF .\" ======================================================================== .\" .IX Title "PERLREREF 1" .TH PERLREREF 1 "2020-07-21" "perl v5.28.1" "Perl Programmers Reference Guide" .\" For nroff, turn off justification. Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .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 ALSO\*(R"\s0 section in this document. .SS "\s-1OPERATORS\s0" .IX Subsection "OPERATORS" \&\f(CW\*(C`=~\*(C'\fR determines to which variable the regex is applied. In its absence, \f(CW$_\fR is used. .PP .Vb 1 \& $var =~ /foo/; .Ve .PP \&\f(CW\*(C`!~\*(C'\fR 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. .PP .Vb 1 \& $var !~ /foo/; .Ve .PP \&\f(CW\*(C`m/pattern/msixpogcdualn\*(C'\fR searches a string for a pattern match, applying the given options. .PP .Vb 10 \& m Multiline mode \- ^ and $ match internal lines \& s match as a Single line \- . matches \en \& i case\-Insensitive \& x eXtended legibility \- free whitespace and comments \& p Preserve a copy of the matched string \- \& ${^PREMATCH}, ${^MATCH}, ${^POSTMATCH} will be defined. \& o compile pattern Once \& g Global \- all occurrences \& c don\*(Aqt reset pos on failed matches when using /g \& a restrict \ed, \es, \ew and [:posix:] to match ASCII only \& aa (two a\*(Aqs) also /i matches exclude ASCII/non\-ASCII \& l match according to current locale \& u match according to Unicode rules \& d match according to native rules unless something indicates \& Unicode \& n Non\-capture mode. Don\*(Aqt let () fill in $1, $2, etc... .Ve .PP If 'pattern' is an empty string, the last \fIsuccessfully\fR matched regex is used. Delimiters other than '/' may be used for both this operator and the following ones. The leading \f(CW\*(C`m\*(C'\fR can be omitted if the delimiter is '/'. .PP \&\f(CW\*(C`qr/pattern/msixpodualn\*(C'\fR lets you store a regex in a variable, or pass one around. Modifiers as for \f(CW\*(C`m//\*(C'\fR, and are stored within the regex. .PP \&\f(CW\*(C`s/pattern/replacement/msixpogcedual\*(C'\fR substitutes matches of \&'pattern' with 'replacement'. Modifiers as for \f(CW\*(C`m//\*(C'\fR, with two additions: .PP .Vb 2 \& e Evaluate \*(Aqreplacement\*(Aq as an expression \& r Return substitution and leave the original string untouched. .Ve .PP \&'e' may be specified multiple times. 'replacement' is interpreted as a double quoted string unless a single-quote (\f(CW\*(C`\*(Aq\*(C'\fR) is the delimiter. .PP \&\f(CW\*(C`m?pattern?\*(C'\fR is like \f(CW\*(C`m/pattern/\*(C'\fR but matches only once. No alternate delimiters can be used. Must be reset with \fBreset()\fR. .SS "\s-1SYNTAX\s0" .IX Subsection "SYNTAX" .Vb 10 \& \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 \& \eg1 or \eg{1}, \eg2 ... Matches the text from the Nth group \& \e1, \e2, \e3 ... Matches the text from the Nth group \& \eg\-1 or \eg{\-1}, \eg\-2 ... Matches the text from the Nth previous group \& \eg{name} Named backreference \& \ek Named backreference \& \ek\*(Aqname\*(Aq Named backreference \& (?P=name) Named backreference (python syntax) .Ve .SS "\s-1ESCAPE SEQUENCES\s0" .IX Subsection "ESCAPE SEQUENCES" These work as in normal strings. .PP .Vb 10 \& \ea Alarm (beep) \& \ee Escape \& \ef Formfeed \& \en Newline \& \er Carriage return \& \et Tab \& \e037 Char whose ordinal is the 3 octal digits, max \e777 \& \eo{2307} Char whose ordinal is the octal number, unrestricted \& \ex7f Char whose ordinal is the 2 hex digits, max \exFF \& \ex{263a} Char whose ordinal is the hex number, unrestricted \& \ecx Control\-x \& \eN{name} A named Unicode character or character sequence \& \eN{U+263D} A Unicode character by hex ordinal \& \& \el Lowercase next character \& \eu Titlecase next character \& \eL Lowercase until \eE \& \eU Uppercase until \eE \& \eF Foldcase until \eE \& \eQ Disable pattern metacharacters until \eE \& \eE End 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 .SS "\s-1CHARACTER CLASSES\s0" .IX Subsection "CHARACTER CLASSES" .Vb 4 \& [amy] Match \*(Aqa\*(Aq, \*(Aqm\*(Aq or \*(Aqy\*(Aq \& [f\-j] Dash specifies "range" \& [f\-j\-] Dash escaped or at start or end means \*(Aqdash\*(Aq \& [^f\-j] Caret indicates "match any character _except_ these" .Ve .PP The following sequences (except \f(CW\*(C`\eN\*(C'\fR) work within or without a character class. The first six are locale aware, all are Unicode aware. See perllocale and perlunicode for details. .PP .Vb 10 \& \ed A digit \& \eD A nondigit \& \ew A word character \& \eW A non\-word character \& \es A whitespace character \& \eS A non\-whitespace character \& \eh A horizontal whitespace \& \eH A non horizontal whitespace \& \eN A non newline (when not followed by \*(Aq{NAME}\*(Aq;; \& not valid in a character class; equivalent to [^\en]; it\*(Aqs \& like \*(Aq.\*(Aq without /s modifier) \& \ev A vertical whitespace \& \eV A non vertical whitespace \& \eR A generic newline (?>\ev|\ex0D\ex0A) \& \& \epP Match P\-named (Unicode) property \& \ep{...} Match Unicode property with name longer than 1 character \& \ePP Match non\-P \& \eP{...} Match lack of Unicode property with name longer than 1 char \& \eX Match Unicode extended grapheme cluster .Ve .PP \&\s-1POSIX\s0 character classes and their Unicode and Perl equivalents: .PP .Vb 3 \& ASCII\- Full\- \& POSIX range range backslash \& [[:...:]] \ep{...} \ep{...} sequence Description \& \& \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\- \& alnum PosixAlnum XPosixAlnum \*(Aqalpha\*(Aq plus \*(Aqdigit\*(Aq \& alpha PosixAlpha XPosixAlpha Alphabetic characters \& ascii ASCII Any ASCII character \& blank PosixBlank XPosixBlank \eh Horizontal whitespace; \& full\-range also \& written as \& \ep{HorizSpace} (GNU \& extension) \& cntrl PosixCntrl XPosixCntrl Control characters \& digit PosixDigit XPosixDigit \ed Decimal digits \& graph PosixGraph XPosixGraph \*(Aqalnum\*(Aq plus \*(Aqpunct\*(Aq \& lower PosixLower XPosixLower Lowercase characters \& print PosixPrint XPosixPrint \*(Aqgraph\*(Aq plus \*(Aqspace\*(Aq, \& but not any Controls \& punct PosixPunct XPosixPunct Punctuation and Symbols \& in ASCII\-range; just \& punct outside it \& space PosixSpace XPosixSpace \es Whitespace \& upper PosixUpper XPosixUpper Uppercase characters \& word PosixWord XPosixWord \ew \*(Aqalnum\*(Aq + Unicode marks \& + connectors, like \& \*(Aq_\*(Aq (Perl extension) \& xdigit ASCII_Hex_Digit XPosixDigit Hexadecimal digit, \& ASCII\-range is \& [0\-9A\-Fa\-f] .Ve .PP Also, various synonyms like \f(CW\*(C`\ep{Alpha}\*(C'\fR for \f(CW\*(C`\ep{XPosixAlpha}\*(C'\fR; all listed in \*(L"Properties accessible through \ep{} and \eP{}\*(R" in perluniprops .PP Within a character class: .PP .Vb 3 \& POSIX traditional Unicode \& [:digit:] \ed \ep{Digit} \& [:^digit:] \eD \eP{Digit} .Ve .SS "\s-1ANCHORS\s0" .IX Subsection "ANCHORS" All are zero-width assertions. .PP .Vb 11 \& ^ Match string start (or line, if /m is used) \& $ Match string end (or line, if /m is used) or before newline \& \eb{} Match boundary of type specified within the braces \& \eB{} Match wherever \eb{} doesn\*(Aqt match \& \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 \& \eK Keep the stuff left of the \eK, don\*(Aqt include it in $& .Ve .SS "\s-1QUANTIFIERS\s0" .IX Subsection "QUANTIFIERS" Quantifiers are greedy by default and match the \fBlongest\fR leftmost. .PP .Vb 9 \& Maximal Minimal Possessive Allowed range \& \-\-\-\-\-\-\- \-\-\-\-\-\-\- \-\-\-\-\-\-\-\-\-\- \-\-\-\-\-\-\-\-\-\-\-\-\- \& {n,m} {n,m}? {n,m}+ Must occur at least n times \& but no more than m times \& {n,} {n,}? {n,}+ Must occur at least n times \& {n} {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 The possessive forms (new in Perl 5.10) prevent backtracking: what gets matched by a pattern with a possessive quantifier will not be backtracked into, even if that causes the whole match to fail. .PP There is no quantifier \f(CW\*(C`{,n}\*(C'\fR. That's interpreted as a literal string. .SS "\s-1EXTENDED CONSTRUCTS\s0" .IX Subsection "EXTENDED CONSTRUCTS" .Vb 10 \& (?#text) A comment \& (?:...) Groups subexpressions without capturing (cluster) \& (?pimsx\-imsx:...) Enable/disable option (as per m// modifiers) \& (?=...) Zero\-width positive lookahead assertion \& (?*pla:...) Same; avail experimentally starting in 5.28 \& (?!...) Zero\-width negative lookahead assertion \& (?*nla:...) Same; avail experimentally starting in 5.28 \& (?<=...) Zero\-width positive lookbehind assertion \& (?*plb:...) Same; avail experimentally starting in 5.28 \& (?...) Grab what we can, prohibit backtracking \& (?*atomic:...) Same; avail experimentally starting in 5.28 \& (?|...) Branch reset \& (?...) Named capture \& (?\*(Aqname\*(Aq...) Named capture \& (?P...) Named capture (python syntax) \& (?[...]) Extended bracketed character class \& (?{ code }) Embedded code, return value becomes $^R \& (??{ code }) Dynamic regex, return value used as regex \& (?N) Recurse into subpattern number N \& (?\-N), (?+N) Recurse into Nth previous/next subpattern \& (?R), (?0) Recurse at the beginning of the whole pattern \& (?&name) Recurse into a named subpattern \& (?P>name) Recurse into a named subpattern (python syntax) \& (?(cond)yes|no) \& (?(cond)yes) Conditional expression, where "cond" can be: \& (?=pat) lookahead \& (?!pat) negative lookahead \& (?<=pat) lookbehind \& (?) named subpattern has matched something \& (\*(Aqname\*(Aq) named subpattern has matched something \& (?{code}) code condition \& (R) true if recursing \& (RN) true if recursing into Nth subpattern \& (R&name) true if recursing into named subpattern \& (DEFINE) always false, no no\-pattern allowed .Ve .SS "\s-1VARIABLES\s0" .IX Subsection "VARIABLES" .Vb 1 \& $_ Default variable for operators to use \& \& $\` Everything prior to matched string \& $& Entire matched string \& $\*(Aq Everything after to matched string \& \& ${^PREMATCH} Everything prior to matched string \& ${^MATCH} Entire matched string \& ${^POSTMATCH} Everything after to matched string .Ve .PP Note to those still using Perl 5.18 or earlier: The use of \f(CW\*(C`$\`\*(C'\fR, \f(CW$&\fR or \f(CW\*(C`$\*(Aq\*(C'\fR will slow down \fBall\fR regex use within your program. Consult perlvar for \f(CW\*(C`@\-\*(C'\fR to see equivalent expressions that won't cause slow down. See also Devel::SawAmpersand. Starting with Perl 5.10, you can also use the equivalent variables \f(CW\*(C`${^PREMATCH}\*(C'\fR, \f(CW\*(C`${^MATCH}\*(C'\fR and \f(CW\*(C`${^POSTMATCH}\*(C'\fR, but for them to be defined, you have to specify the \f(CW\*(C`/p\*(C'\fR (preserve) modifier on your regular expression. In Perl 5.20, the use of \f(CW\*(C`$\`\*(C'\fR, \f(CW$&\fR and \f(CW\*(C`$\*(Aq\*(C'\fR makes no speed difference. .PP .Vb 8 \& $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 \& %+ Named capture groups \& %\- Named capture groups, as array refs .Ve .PP Captured groups are numbered according to their \fIopening\fR paren. .SS "\s-1FUNCTIONS\s0" .IX Subsection "FUNCTIONS" .Vb 5 \& lc Lowercase a string \& lcfirst Lowercase first char of a string \& uc Uppercase a string \& ucfirst Titlecase first char of a string \& fc Foldcase a string \& \& pos Return or set current match position \& quotemeta Quote metacharacters \& reset Reset m?pattern? status \& study Analyze string for optimizing matching \& \& split Use a regex to split a string into parts .Ve .PP The first five 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, \f(CW\*(C`\eu\*(C'\fR, and \f(CW\*(C`\eF\*(C'\fR. For Titlecase, see \*(L"Titlecase\*(R"; For Foldcase, see \*(L"Foldcase\*(R". .SS "\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. .PP \fIFoldcase\fR .IX Subsection "Foldcase" .PP Unicode form that is useful when comparing strings regardless of case, as certain characters have complex one-to-many case mappings. Primarily a variant of lowercase. .SH "AUTHOR" .IX Header "AUTHOR" Iain Truskett. Updated by the Perl 5 Porters. .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 perlrebackslash for a reference on backslash sequences. .IP "\(bu" 4 perlrecharclass for a reference on character classes. .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 perllocale for details on regexes and internationalisation. .IP "\(bu" 4 \&\fIMastering Regular Expressions\fR by Jeffrey Friedl () 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.