I do want to check out Moose and MooseX (I'm tempted to call it 'Moose++'), it seems like alot of people use it. But I first want to get thru the, err, 'official' implementation of OO Perl as described in the Alpaca book.
As I was reading the book and got to the section on closures, I thought to myself: "Ahh, this is how they are going to do private variables in a class." Then it turns out that it doesn't work that way at all. The private data is just all the fields in the whatever-it-is that the blessed reference references. And some people complain that it isn't as really private as they'd like.
I'm surprised that there is not more use of closures. OTOH, maybe that would not work well with inheritance? In Googling about on the issue I see that I'm far from the first person to think about this. Well, exploring that question is likely much further over my head at this point than is Moose.