Not really hints on how to optimise, more hints on how to avoid a lot of problems with it. Make sure your code works beforehand, and use unit tests such as Test::More, or Test::Harness to make sure your code remains working whilst you're torturing it. Yes, there are rather a lot more of them to chose from if you look.. this is one wheel important enough that it's worth having a few choices as to what colour you want.
Oh, and make sure you know the output from your profiler. There's nothing worse than optimising the wrong part.
<CITE>"Premature optimization is the root of all evil."
- Donald Knuth</CITE>