When learning regexes, or when you need to use a feature you have not used yet or don't use often, it can be quite useful to have a place for quick look-up. I hope this Regex Cheat-sheet will provide such aid for you.

Introduction to regexes in Perl

a Just an 'a' character . Any character except new-line

Character Classes

Regex Character Classes and Special Character classes.

[bgh.] One of the characters listed in the character class b,g,h or . in this case. [b-h] The same as [bcdefgh]. [a-z] Lower case Latin letters. [bc-] The characters b, c or - (dash). [^bx] Complementary character class. Anything except b or x. \w Word characters: [a-zA-Z0-9_]. \d Digits: [0-9] \s [\f\t

\r ] form-feed, tab, newline, carriage return and SPACE \W The complementary of \w: [^\w] \D [^\d] \S [^\s] [:class:] POSIX character classes (alpha, alnum...) \p{...} Unicode definitions (IsAlpha, IsLower, IsHebrew, ...) \P{...} Complementary Unicode character classes.

TODO: add examples \w and \d matching unicode letters and numebers.

Quantifiers

Regex Quantifiers

a? 0-1 'a' characters a+ 1-infinite 'a' characters a* 0-infinite 'a' characters a{n,m} n-m 'a' characters a{n,} n-infinite 'a' characters a{n} n 'a' characters

"Quantifier-modifier" aka. Minimal Matching

a+? a*? a{n,m}? a{n,}? a?? a{n}?

Other

| Alternation

Grouping and capturing

(...) Grouping and capturing \1, \2, \3, \4 ... Capture buffers during regex matching $1, $2, $3, $4 ... Capture variables after successful matching (?:...) Group without capturing (don't set \1 nor $1)

Anchors

^ Beginning of string (or beginning of line if /m enabled) $ End of string (or end of line if /m enabled) \A Beginning of string \Z End of string (or before new-line) \z End of string \b Word boundary (start-of-word or end-of-word) \G Match only at pos(): at the end-of-match position of prior m//g

Modifiers

/m Change ^ and $ to match beginning and end of line respectively /s Change . to match new-line as well /i Case insensitive pattern matching /x Extended pattern (disregard white-space, allow comments starting with #)

Extended

(?#text) Embedded comment (?adlupimsx-imsx) One or more embedded pattern-match modifiers, to be turned on or off. (?:pattern) Non-capturing group. (?|pattern) Branch test. (?=pattern) A zero-width positive look-ahead assertion. (?!pattern) A zero-width negative look-ahead assertion. (?<=pattern) A zero-width positive look-behind assertion. (?<!pattern) A zero-width negative look-behind assertion.

(?'NAME'pattern) (?<NAME>pattern) A named capture group. \k<NAME> \k'NAME' Named backreference.

(?{ code }) Zero-width assertion with code execution. (??{ code }) A "postponed" regular subexpression with code execution.

Other Regex related articles

Official documentation