Start with smaller examples to become more familiar with data structures, then grow into the larger ones. perldsc like hippo said is a very good start.

There are also very detailed guides all over the net for maintaining Perl data structures. I wrote a guide to references a few years ago that may help.

One book that I read numerous times (and I reference in my above link) that helped me tremendously which is *well* worth the money is Randal Schwartz's (aka. merlyn) Learning Perl Objects, References and Modules. It's very old, but still very relevant. Considering that I try to make as much of my code as possible compliant back to v5.8, the examples in the book are not much (if at all) different from the techniques still in use today.