I bought a copy of Object Oriented Perl about a week ago and have been working my way through it ever since. I find it much easier to learn things from than Programming Perl (I remember reading the section on objects in PP at least a dozen times before I understood it) as well as being well-written and fairly concise.

It's a small shame the first two chapters are used up explaining perl and OO, and chapter 3 is something of a no-brainer if you've used perl objects before, but from there on in it's pretty much all news. The sections on tie and overloaded operators are espescially good.

I felt the content ramped up fairly quickly (I still don't understand the last three chapters) but builds in a logical manner, making it easy reading. The Quick Reference Guide (Appendix A) is good, but I found Appendix B less useful. (Any book whose index has an entry for Real World wins *my* vote.)