perl-Class-Singleton

This is the Class::Singleton module. A Singleton describes an object class
that can have only one instance in any system. An example of a Singleton
might be a print spooler or system registry. This module implements a
Singleton class from which other classes can be derived. By itself, the
Class::Singleton module does very little other than manage the
instantiation of a single object. In deriving a class from
Class::Singleton, your module will inherit the Singleton instantiation
method and can implement whatever specific functionality is required.