I too, used to have a bit of trouble wrapping my head around OOP. Tried Java at home, but without any real projects, it was just playing, and nothing sunk in.

So what I did was this: I purchased Damian Conway's book on OO Perl, and took in as much as I could. Then, for my next couple of Perl projects, I used OO rather than procedural logic, even though OO wasn't really required. It just forced me to get used to the idiom, and when I got stuck, I'd return to D's book. Now, when I use Java or even C#, I'm easily splip into OO mode.

(BTW: now that I've got what I needed out of OO Perl, I don't use it that much. I like it, but my work generally requires me to knock up quick scripts, and OO Perl isn't really required. However, I'm grateful to the CPAN contributors who offer OO interfaces -- they make my life easier)