The current implementation is based on ideas [publicized][cox] by Russ Cox.

The original implementation was inspired and heavily based on the ideas from ["A
Play on Regular Expressions"][play] by Sebastian Fischer, Frank Huch and Thomas
Wilke.

[cox]: http://swtch.com/~rsc/regexp/
[play]: http://sebfisch.github.com/haskell-regexp/regexp-play.pdf