Oniguruma

Oniguruma (鬼車) by K. Kosako is a BSD licensed regular expression library that supports a variety of character encodings. The Ruby programming language, in version 1.9, as well as PHP's multi-byte string module (since PHP5), use Oniguruma as their regular expression engine. It is also used in products such as Atom, Take Command Console, Tera Term, TextMate, Sublime Text and SubEthaEdit. Oniguruma is Japanese for "Oni's Chariot".

There is also a forked Oniguruma version called "Onigmo" (Oniguruma-mod) which includes some features introduced in Perl 5.10+. Ruby since version 2.0 has also switched to it and features have been backported from ruby to Onigmo.