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Special characters in regular expressions
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| . | matches an arbitrary character, but not a newline unless it is a single-line match (see m//s). |
| (...) | groups a series of pattern elements to a single element. |
| ^ | matches the beginning of the target. In multiline mode (see m//m) also matches after every newline character. |
| $ | matches the end of the line. In multiline mode also matches before every newline character. |
| [ ... ] | denotes a class of characters to match. [^ ... ] negates the class. |
| ( ... | ... | ... ) | matches one of the alternatives. |
| (?# TEXT ) | Comment. |
| (?: REGEXP ) | Like (REGEXP) but does not make back-references. |
| (?= REGEXP ) | Zero width positive look-ahead assertion. |
| (?! REGEXP ) | Zero width negative look-ahead assertion. |
| (? MODIFIER ) | Embedded pattern-match modifier. MODIFIER can be one or more of i, m, s, or x. |
Quantified subpatterns match as many times as possible. When followed with a ? they match the minimum number of times. These are the quantifiers: | |
| + | matches the preceding pattern element one or more times. |
| ? | matches zero or one times. |
| * | matches zero or more times. |
| {N,M} | denotes the minimum N and maximum M match count. {N} means exactly N times; {N,} means at least N times. |
A \ escapes any special meaning of the following character if non-alphanumeric, but it turns most alphanumeric characters into something special: | |
| \w | matches alphanumeric, including _, \W matches non-alphanumeric. |
| \s | matches whitespace, \S matches non-whitespace. |
| \d | matches numeric, \D matches non-numeric. |
| \A | matches the beginning of the string, \Z matches the end. |
| \b | matches word boundaries, \B matches non-boundaries. |
| \G | matches where the previous m//g search left off. |
| \n, \r, \f, \t | etc. have their usual meaning. |
| \w, \s and \d | may be used within character classes, \b denotes backspace in this context. |
Back-references: | |
| \1 ... \9 | refer to matched subexpressions, grouped with (), inside the match. |
| \10 | and up can also be used if the pattern matches that many subexpressions. |
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