Re^3: Please evaluate: RegEx for validating e-mail addresses

[FoxtrotUniform]

I've only spent a few minutes looking for it, but my 2nd-edition Mastering Regular Expressions doesn't seem to include that regex. So I can't check my suspicion that the original MRE regex didn't actually match all RFC822 addresses, just most of them - I vaguely remember a disclaimer about comments in hostnames not being recognized, or some such. (Probably something recursive, now that I think about it.) Even Ovid's monstrous regex may not be complete.

[merlyn]

Yes, you remember almost correctly! The problem is nested comments. The oft-quoted monster regex deals with all comments, but no nested comments. Nested comments are impossible without resorting to trickery (a regex that only Perl could do because it has embedded Perl code).

[tachyon]

From memory the regex itself was not included per se (vol 1). It was presented as an algorithm to generate it dynamically. This code is still available online on Jeffrey Friedls website