BUU has asked for the wisdom of the Perl Monks concerning the following question:

I was hanging out on irc (freenode, #perl) this morning chatting about this and that, mostly about crappy programming languages and so forth. Someone entering the conversation mentioned that once he sat on a class of VB students who had to write a tic-tac-toe "gui" in VB, no AI, just checking for win conditions. He recounted that all of the students solved the problem by writing 16 or 20 or however many lines of code that looked like:
if( $board[0][0] eq 'x' and $board[0][1] eq 'x' and $board[0][2] eq 'x +' ) { #win! }
Or whatever the VB equivalent happened to be. Naturally, as a Perl programmer who strives to be as concise as possible (while still being clear and understandable of course), I was horrified by all the repeated code. But then when I stopped to think how I would do it, I had problems coming up with a way that was substantially better. So I pose the question to you: Given a datastructure, how do you check for a tic-tac-toe win condition?

Feel free to assume any data structure, I have arbitrarily decided the default datastructure will be a 2d array containing 'x's, 'o's and 'undefs', whose meaning should be obvious. Using a different one is perfectly acceptable, just make sure you describe said datastructure.

(And yes, I promise I'm not going to steal *anybody's* hard work and fraudently use it to gain a job. Not that I'm bitter. This "challenge" has nothing to do with anything in the real world and is merely the result of a late night conversation on IRC.)