I don't know about Perl proper, but PCRE does have an automaton option (which the docs call a DFA but, if I remember correctly, is actually an NFA). In practic

I don't know about Perl proper, but PCRE does have an automaton option (which the docs call a DFA but, if I remember correctly, is actually an NFA). In practice, the vast majority of production regexen don't require backreferences or generalized assertions, so automata are an attractive option. This is particularly true for security applications (e.g. firewalls/NIDS) and public-facing services like Google Code Search. I wouldn't be surprised if people were attacking Snort boxes via PCRE, for example.