Regular expressions (orregex) are rules that govern which sequences of characters come up in a search.

Regular expressions are implemented in various languages, but the best-known implementation is the Perl Implementation, which has given rise to its own ecosystem of implementations called PCRE (Perl Compatible Regular Expression). On the Web,JavaScript provides another regex implementation through theRegExp object.

See also

• Regular expressions on Wikipedia
• Interactive tutorial
• Visualized Regular Expression
• Writing regular expressions in JavaScript