So, assuming you're already mildly familiar with Perl, but don't know what OOP in general is, I whole-heartily recommend you to read the over-cited book "Object Oriented Perl" by Damian Conway. That book is not only a very good book about Perl's OOP concepts and techniques, it's really one of the best book written about OOP in the CS field, and I've read many on the subject.
That book is so good, that even if you're a beginner in Perl and don't know what a reference is, it is a self-contained manual on the subject, and by the second chapter will teach you all the concepts and language features necessary to start building Perl classes and more! It is that good!
Also consider this: while the more Perl modern approach is to use one of the many OO frameworks/libs available (Moose,Mouse,Moo,etc..), consider that the core of those frameworks is built upon the tools and techniques available in Perl 5, which are clearly described in Damian's book.
Knowing at least some of those things, you won't then be scared or disoriented when reading Moose's manual about refs or blessing, or packages.
And you will also able to interpret to some extent error and debug messages when things will inevitably go wrong for some reason.
You can of course start today making Perl classes using Moose and referring to its manual, but to put to use it (and maybe starting to use some OO software patterns) you'd have some general OO knowledge, and that book will give also that.
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