I am learning to use Perl's Object Oriented Programming facilities. Its a bit different from what I was used to in C/C++.
For one thing, the entire OOP framework in Perl is a chimera, built out of namespace hacks in the interpreter.
Once you get your head around that, there's no stopping you.
I'm still struggling with some advanced concepts, so won't talk about them now, but let's start with the basics.