If you're greedy and hadn't enough from the posts above, José's Guide for creating Perl modules will help you pass some time learning. If you are really hungry, try also to take a look at "Modules: Creation, Use, and Abuse" in perlmodlib.

For books, you can try to download a free copy of "Writing Perl Modules for CPAN" from the publisher's site. Don't know why they link only the first chapter in the book's description page while they give the whole book for free. At last, if you also want to put your meatspace hands on something, in addition to the previous book you can go for Learning Perl Objects, References and Modules.

With this, you should have to eat for a while...