I'd suggest as a starting point the perlmod documentation. Once you've read that, look at the other documentation that it links to. After that, you might try the book 'Learning Perl Objects, References & Modules', or if it's specifically an OO module, 'Object Oriented Perl'.

For the efficiency side of things, I find that's a much harder thing to teach. (I look at it, to a certain degree, to be more of an art than a science), and tuning is a never ending process that involves too many variables (input characteristcs, memory, cpu power, disk i/o, etc.) to be solved absolutely. Perhaps someone else can give advice on this topic.