| 1 | =head1 NAME |
| 2 | |
| 3 | perlreref - Perl Regular Expressions Reference |
| 4 | |
| 5 | =head1 DESCRIPTION |
| 6 | |
| 7 | This is a quick reference to Perl's regular expressions. |
| 8 | For full information see L<perlre> and L<perlop>, as well |
| 9 | as the L</"SEE ALSO"> section in this document. |
| 10 | |
| 11 | =head2 OPERATORS |
| 12 | |
| 13 | =~ determines to which variable the regex is applied. |
| 14 | In its absence, $_ is used. |
| 15 | |
| 16 | $var =~ /foo/; |
| 17 | |
| 18 | !~ determines to which variable the regex is applied, |
| 19 | and negates the result of the match; it returns |
| 20 | false if the match succeeds, and true if it fails. |
| 21 | |
| 22 | $var !~ /foo/; |
| 23 | |
| 24 | m/pattern/igmsoxc searches a string for a pattern match, |
| 25 | applying the given options. |
| 26 | |
| 27 | i case-Insensitive |
| 28 | g Global - all occurrences |
| 29 | m Multiline mode - ^ and $ match internal lines |
| 30 | s match as a Single line - . matches \n |
| 31 | o compile pattern Once |
| 32 | x eXtended legibility - free whitespace and comments |
| 33 | c don't reset pos on failed matches when using /g |
| 34 | |
| 35 | If 'pattern' is an empty string, the last I<successfully> matched |
| 36 | regex is used. Delimiters other than '/' may be used for both this |
| 37 | operator and the following ones. |
| 38 | |
| 39 | qr/pattern/imsox lets you store a regex in a variable, |
| 40 | or pass one around. Modifiers as for m// and are stored |
| 41 | within the regex. |
| 42 | |
| 43 | s/pattern/replacement/igmsoxe substitutes matches of |
| 44 | 'pattern' with 'replacement'. Modifiers as for m// |
| 45 | with one addition: |
| 46 | |
| 47 | e Evaluate replacement as an expression |
| 48 | |
| 49 | 'e' may be specified multiple times. 'replacement' is interpreted |
| 50 | as a double quoted string unless a single-quote (') is the delimiter. |
| 51 | |
| 52 | ?pattern? is like m/pattern/ but matches only once. No alternate |
| 53 | delimiters can be used. Must be reset with L<reset|perlfunc/reset>. |
| 54 | |
| 55 | =head2 SYNTAX |
| 56 | |
| 57 | \ Escapes the character immediately following it |
| 58 | . Matches any single character except a newline (unless /s is used) |
| 59 | ^ Matches at the beginning of the string (or line, if /m is used) |
| 60 | $ Matches at the end of the string (or line, if /m is used) |
| 61 | * Matches the preceding element 0 or more times |
| 62 | + Matches the preceding element 1 or more times |
| 63 | ? Matches the preceding element 0 or 1 times |
| 64 | {...} Specifies a range of occurrences for the element preceding it |
| 65 | [...] Matches any one of the characters contained within the brackets |
| 66 | (...) Groups subexpressions for capturing to $1, $2... |
| 67 | (?:...) Groups subexpressions without capturing (cluster) |
| 68 | | Matches either the subexpression preceding or following it |
| 69 | \1, \2 ... The text from the Nth group |
| 70 | |
| 71 | =head2 ESCAPE SEQUENCES |
| 72 | |
| 73 | These work as in normal strings. |
| 74 | |
| 75 | \a Alarm (beep) |
| 76 | \e Escape |
| 77 | \f Formfeed |
| 78 | \n Newline |
| 79 | \r Carriage return |
| 80 | \t Tab |
| 81 | \037 Any octal ASCII value |
| 82 | \x7f Any hexadecimal ASCII value |
| 83 | \x{263a} A wide hexadecimal value |
| 84 | \cx Control-x |
| 85 | \N{name} A named character |
| 86 | |
| 87 | \l Lowercase next character |
| 88 | \u Titlecase next character |
| 89 | \L Lowercase until \E |
| 90 | \U Uppercase until \E |
| 91 | \Q Disable pattern metacharacters until \E |
| 92 | \E End case modification |
| 93 | |
| 94 | For Titlecase, see L</Titlecase>. |
| 95 | |
| 96 | This one works differently from normal strings: |
| 97 | |
| 98 | \b An assertion, not backspace, except in a character class |
| 99 | |
| 100 | =head2 CHARACTER CLASSES |
| 101 | |
| 102 | [amy] Match 'a', 'm' or 'y' |
| 103 | [f-j] Dash specifies "range" |
| 104 | [f-j-] Dash escaped or at start or end means 'dash' |
| 105 | [^f-j] Caret indicates "match any character _except_ these" |
| 106 | |
| 107 | The following sequences work within or without a character class. |
| 108 | The first six are locale aware, all are Unicode aware. The default |
| 109 | character class equivalent are given. See L<perllocale> and |
| 110 | L<perlunicode> for details. |
| 111 | |
| 112 | \d A digit [0-9] |
| 113 | \D A nondigit [^0-9] |
| 114 | \w A word character [a-zA-Z0-9_] |
| 115 | \W A non-word character [^a-zA-Z0-9_] |
| 116 | \s A whitespace character [ \t\n\r\f] |
| 117 | \S A non-whitespace character [^ \t\n\r\f] |
| 118 | |
| 119 | \C Match a byte (with Unicode, '.' matches a character) |
| 120 | \pP Match P-named (Unicode) property |
| 121 | \p{...} Match Unicode property with long name |
| 122 | \PP Match non-P |
| 123 | \P{...} Match lack of Unicode property with long name |
| 124 | \X Match extended unicode sequence |
| 125 | |
| 126 | POSIX character classes and their Unicode and Perl equivalents: |
| 127 | |
| 128 | alnum IsAlnum Alphanumeric |
| 129 | alpha IsAlpha Alphabetic |
| 130 | ascii IsASCII Any ASCII char |
| 131 | blank IsSpace [ \t] Horizontal whitespace (GNU extension) |
| 132 | cntrl IsCntrl Control characters |
| 133 | digit IsDigit \d Digits |
| 134 | graph IsGraph Alphanumeric and punctuation |
| 135 | lower IsLower Lowercase chars (locale and Unicode aware) |
| 136 | print IsPrint Alphanumeric, punct, and space |
| 137 | punct IsPunct Punctuation |
| 138 | space IsSpace [\s\ck] Whitespace |
| 139 | IsSpacePerl \s Perl's whitespace definition |
| 140 | upper IsUpper Uppercase chars (locale and Unicode aware) |
| 141 | word IsWord \w Alphanumeric plus _ (Perl extension) |
| 142 | xdigit IsXDigit [0-9A-Fa-f] Hexadecimal digit |
| 143 | |
| 144 | Within a character class: |
| 145 | |
| 146 | POSIX traditional Unicode |
| 147 | [:digit:] \d \p{IsDigit} |
| 148 | [:^digit:] \D \P{IsDigit} |
| 149 | |
| 150 | =head2 ANCHORS |
| 151 | |
| 152 | All are zero-width assertions. |
| 153 | |
| 154 | ^ Match string start (or line, if /m is used) |
| 155 | $ Match string end (or line, if /m is used) or before newline |
| 156 | \b Match word boundary (between \w and \W) |
| 157 | \B Match except at word boundary (between \w and \w or \W and \W) |
| 158 | \A Match string start (regardless of /m) |
| 159 | \Z Match string end (before optional newline) |
| 160 | \z Match absolute string end |
| 161 | \G Match where previous m//g left off |
| 162 | |
| 163 | =head2 QUANTIFIERS |
| 164 | |
| 165 | Quantifiers are greedy by default -- match the B<longest> leftmost. |
| 166 | |
| 167 | Maximal Minimal Allowed range |
| 168 | ------- ------- ------------- |
| 169 | {n,m} {n,m}? Must occur at least n times but no more than m times |
| 170 | {n,} {n,}? Must occur at least n times |
| 171 | {n} {n}? Must occur exactly n times |
| 172 | * *? 0 or more times (same as {0,}) |
| 173 | + +? 1 or more times (same as {1,}) |
| 174 | ? ?? 0 or 1 time (same as {0,1}) |
| 175 | |
| 176 | There is no quantifier {,n} -- that gets understood as a literal string. |
| 177 | |
| 178 | =head2 EXTENDED CONSTRUCTS |
| 179 | |
| 180 | (?#text) A comment |
| 181 | (?imxs-imsx:...) Enable/disable option (as per m// modifiers) |
| 182 | (?=...) Zero-width positive lookahead assertion |
| 183 | (?!...) Zero-width negative lookahead assertion |
| 184 | (?<=...) Zero-width positive lookbehind assertion |
| 185 | (?<!...) Zero-width negative lookbehind assertion |
| 186 | (?>...) Grab what we can, prohibit backtracking |
| 187 | (?{ code }) Embedded code, return value becomes $^R |
| 188 | (??{ code }) Dynamic regex, return value used as regex |
| 189 | (?(cond)yes|no) cond being integer corresponding to capturing parens |
| 190 | (?(cond)yes) or a lookaround/eval zero-width assertion |
| 191 | |
| 192 | =head2 VARIABLES |
| 193 | |
| 194 | $_ Default variable for operators to use |
| 195 | $* Enable multiline matching (deprecated; not in 5.9.0 or later) |
| 196 | |
| 197 | $& Entire matched string |
| 198 | $` Everything prior to matched string |
| 199 | $' Everything after to matched string |
| 200 | |
| 201 | The use of those last three will slow down B<all> regex use |
| 202 | within your program. Consult L<perlvar> for C<@LAST_MATCH_START> |
| 203 | to see equivalent expressions that won't cause slow down. |
| 204 | See also L<Devel::SawAmpersand>. |
| 205 | |
| 206 | $1, $2 ... hold the Xth captured expr |
| 207 | $+ Last parenthesized pattern match |
| 208 | $^N Holds the most recently closed capture |
| 209 | $^R Holds the result of the last (?{...}) expr |
| 210 | @- Offsets of starts of groups. $-[0] holds start of whole match |
| 211 | @+ Offsets of ends of groups. $+[0] holds end of whole match |
| 212 | |
| 213 | Captured groups are numbered according to their I<opening> paren. |
| 214 | |
| 215 | =head2 FUNCTIONS |
| 216 | |
| 217 | lc Lowercase a string |
| 218 | lcfirst Lowercase first char of a string |
| 219 | uc Uppercase a string |
| 220 | ucfirst Titlecase first char of a string |
| 221 | |
| 222 | pos Return or set current match position |
| 223 | quotemeta Quote metacharacters |
| 224 | reset Reset ?pattern? status |
| 225 | study Analyze string for optimizing matching |
| 226 | |
| 227 | split Use regex to split a string into parts |
| 228 | |
| 229 | The first four of these are like the escape sequences C<\L>, C<\l>, |
| 230 | C<\U>, and C<\u>. For Titlecase, see L</Titlecase>. |
| 231 | |
| 232 | =head2 TERMINOLOGY |
| 233 | |
| 234 | =head3 Titlecase |
| 235 | |
| 236 | Unicode concept which most often is equal to uppercase, but for |
| 237 | certain characters like the German "sharp s" there is a difference. |
| 238 | |
| 239 | =head1 AUTHOR |
| 240 | |
| 241 | Iain Truskett. |
| 242 | |
| 243 | This document may be distributed under the same terms as Perl itself. |
| 244 | |
| 245 | =head1 SEE ALSO |
| 246 | |
| 247 | =over 4 |
| 248 | |
| 249 | =item * |
| 250 | |
| 251 | L<perlretut> for a tutorial on regular expressions. |
| 252 | |
| 253 | =item * |
| 254 | |
| 255 | L<perlrequick> for a rapid tutorial. |
| 256 | |
| 257 | =item * |
| 258 | |
| 259 | L<perlre> for more details. |
| 260 | |
| 261 | =item * |
| 262 | |
| 263 | L<perlvar> for details on the variables. |
| 264 | |
| 265 | =item * |
| 266 | |
| 267 | L<perlop> for details on the operators. |
| 268 | |
| 269 | =item * |
| 270 | |
| 271 | L<perlfunc> for details on the functions. |
| 272 | |
| 273 | =item * |
| 274 | |
| 275 | L<perlfaq6> for FAQs on regular expressions. |
| 276 | |
| 277 | =item * |
| 278 | |
| 279 | The L<re> module to alter behaviour and aid |
| 280 | debugging. |
| 281 | |
| 282 | =item * |
| 283 | |
| 284 | L<perldebug/"Debugging regular expressions"> |
| 285 | |
| 286 | =item * |
| 287 | |
| 288 | L<perluniintro>, L<perlunicode>, L<charnames> and L<locale> |
| 289 | for details on regexes and internationalisation. |
| 290 | |
| 291 | =item * |
| 292 | |
| 293 | I<Mastering Regular Expressions> by Jeffrey Friedl |
| 294 | (F<http://regex.info/>) for a thorough grounding and |
| 295 | reference on the topic. |
| 296 | |
| 297 | =back |
| 298 | |
| 299 | =head1 THANKS |
| 300 | |
| 301 | David P.C. Wollmann, |
| 302 | Richard Soderberg, |
| 303 | Sean M. Burke, |
| 304 | Tom Christiansen, |
| 305 | Jim Cromie, |
| 306 | and |
| 307 | Jeffrey Goff |
| 308 | for useful advice. |
| 309 | |
| 310 | =cut |