Aspect::Library::Singleton - A singleton aspect


  use Aspect;
  use Aspect::Singleton;
  aspect Singleton => 'Foo::new';
  my $f1 = Foo->new;
  my $f2 = Foo->new;
  # Both $f1 and $f2 refer to the same object


A reusable aspect that forces singleton behavior on a constructor. The constructor is defined by a pointcut spec: a string. regexp, or code ref.

It is slightly different from Class::Singleton (

  • No specific name requirement on the constructor for the external interface, or for the implementation (Class::Singleton requires clients use instance(), and that subclasses override _new_instance()). With aspects, you can change the cardinality of your objects without changing the clients, or the objects themselves.

  • No need to inherit from anything- use pointcuts to specify the constructors you want to memoize. Instead of pulling singleton behavior from a base class, you are pushing it in, using the aspect.

  • No package variable or method is added to the callers namespace

Note that this is just a special case of memoizing.


Adam Kennedy <>

Marcel Grünauer <>

Ran Eilam <>


Copyright 2001 by Marcel Grünauer

Some parts copyright 2009 - 2013 Adam Kennedy.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.