ObjectOrientedPerl by DamianConway.
ISBN: 1-88477-779-1 A guide to ObjectOrientedProgramming in PerlLanguage. One of the DefinitivePerlBooks.
Site: http://www.manning.com/Conway/
I'm currently working my way through this, and I can testify that Damian is an excellent teacher. A lot of things that I previously found impenetrable are now clear to me.