Consider an expression that evaluates as true if and only if $_ contains a 2-character U.S. state abbreviation. One way would be to enumerate them: /^(AK|AL|AR ... )$/. A shorter way might be to fold out the first letter. But, what about cool tricks? Perhaps there is a truely short awsome and cool solution. So I toss it into the ring for the perlwits here.

—John