Moose is an extension of the object system of the Perl programming language. It brings modern object-oriented language features to Perl 5, making object-oriented Perl programming more consistent and less tedious.
The main goal of Moose is to make Perl 5 Object Oriented programming easier, more consistent, and less tedious. With Moose you can think more about what you want to do and less about the mechanics of OOP.
Additionally, Moose is built on top of Class::MOP, which is a metaclass system for Perl 5. This means that Moose not only makes building normal Perl 5 objects better, but it provides the power of metaclass programming as well.
If you’re new to Moose, the best place to start is the Moose::Manual docs, followed by the Moose::Cookbook. The intro will show you what Moose is, and how it makes Perl 5 OO better.