Perhaps one of the most important things you can do is use benchmark. This can give you an excellent method of comparing how efficient different methods of approaching the same problem are. Examples:

• Benchmarking Your Code by turnstep
• How are we lazy? by Ovid
• Benchmark by root

Learn to live by this module and you will begin to understand things about Perl efficiency that most of us only dream of.

Cheers,
Ovid