A singleton is a class that has only one instance in an application.
'MooseX::Singleton' lets you easily upgrade (or downgrade, as it were) your
the Moose manpage class to a singleton.

All you should need to do to transform your class is to change 'use Moose'
to 'use MooseX::Singleton'. This module uses a new class metaclass and
instance metaclass, so if you're doing metamagic you may not be able to use
this.

'MooseX::Singleton' gives your class an 'instance' method that can be used
to get a handle on the singleton. It's actually just an alias for 'new'.