There are several good resources. For two of them, you need look no further than your own hardrive, if you have perl installed. The perltoot manpage, and the perlboot manpage (perlboot comes with perl 5.6.0 only) are both excellent OO Perl resources. As far as books go, Damian Conway's Object Oriented Perl from Manning Press comes highly recommended, though I personally haven't read it (yet).