regular expression help [port]

[:B nerdy]

Greetings, this is a regular expression for an email address
"^[a-z0-9_]+@[a-z0-9\-]{2,}\.[a-z0-9\-\.]{2,}$"

i wish to valid a variable against this string. would someone be so kind to
supply a few lines of code to do this?

cheers