Moose is an extension of the Perl 5 object system.

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 the Class::MOP manpage, 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.