You might want to read Moose::Manual::MOP if you haven't done so yet.
If you've ever thought "Moose is great, but I wish it did X differently", then you've gone meta. The meta
recipes demonstrate how to change and extend the way Moose works by extending and overriding how the meta
classes (Moose::Meta::Class, Moose::Meta::Attribute, etc) work.
The metaclass API is a set of classes that describe classes, roles, attributes, etc. The metaclass API
lets you ask questions about a class, like "what attributes does it have?", or "what roles does the class
do?"
The metaclass system also lets you make changes to a class, for example by adding new methods or
attributes.
The interface presented by Moose.pm ("has", "with", "extends") is just a thin layer of syntactic sugar
over the underlying metaclass system.
By extending and changing how this metaclass system works, you can create your own Moose variant.
Examples
Let's say that you want to add additional properties to attributes. Specifically, we want to add a
"label" property to each attribute, so we can write "My::Class->meta()->get_attribute('size')->label()".
The first recipe shows how to do this using an attribute trait.
You might also want to add additional properties to your metaclass. For example, if you were writing an
ORM based on Moose, you could associate a table name with each class via the class's metaclass object,
letting you write "My::Class->meta()->table_name()".
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