And this is why whiteboard programming interviews where syntax matters are toxic. I almost have the cojones these days to walk out as soon as they pull that crap, but it's a big red flag to me when they want the REAL regex to validate an e-mail address (though typically asking them if they want "the most naive implementation or the RFC 2822-compliant one" is enough to shut them up.

http://www.regular-expressions.info/email.html if you don't get why this is a bad idea (it's the equiv. of memorizing pi to the thousandth digit).