Aspect::Library::Singleton - A singleton aspect


  use Aspect::Singleton;

  aspect Singleton => 'Foo::new';

  my $f1 = Foo->new;
  my $f2 = Foo->new;

  # now $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.


See the Aspect pods for a guide to the Aspect module.

You can find an example comparing the OO and AOP solutions in the examples/ directory of the distribution.