You should really type perldoc -q address at your nearest console and read the well chosen answer. While DamnDirtyApe has suggested a fine and useful module, it does help to be aware that there really is no way to be certain that an e-mail address will work. Actually that is also repeated in the POD for Email::Valid which also references the PerlFAQ, and the cycle continues...

If you really want to see a regex that attempts this, I recommend Jeffrey Friedl's wonderful (if slightly outdated now) Mastering Regular Expressions which includes a discussion on just such a beast towards the end.

Update: See more good information from larsen at Re: Regex Unexplained Failure in response to a very similar question asked only 20 minutes after yours...

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I'd like to be able to assign to an luser