regexps aren't regular, so most "proper" engines also do backtracking. Indeed, if you stick with the regular subset, you can be really fast: http://swtch.com/

regexps aren't regular, so most "proper" engines also do backtracking. Indeed, if you stick with the regular subset, you can be really fast: http://swtch.com/~rsc/regexp/regexp1.html http://swtch.com/~rsc/regexp/regexp1.html