Great idea! I'd love to pick up more techniques on optimising my code. This would be really valuable to me, and a lot of others here I'm sure, and a lot of the techniques would be immediately applicable to work.
I'm not so interested in the obfuscated perl as, although it is cool, I have to write maintainable code and my co-workers aren't experts (basically I don't want to get into 'bad' habits).
Judging it will be hard as machines/os's will vary in speed, floating point efficiency etc. Shortest version means it currently is pretty easy to work out the winner, does it work and how long is it?
Maybe some use of benchmarking contrasting the versions on your own PC?