Depending on how much work you want to do, I'd think about buying Perl Best Practices and just going through each of the tips/principles and applying them one-by-one. There are over 100. I've been having fun applying the principles to code I'm writing as I read each chapter. I wish I had time to fix it all, but I maintain so many scripts that I and/or myself have written at various stages of expertise that I do a little here and a little there when I can. If you're just concentrating on one big program, I think it would be worth it. A lot of the principles hinge on efficiency just as much as maintainability.