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UNIVERSAL::ref - Turns ref() into a multimethod


  # True! Wrapper pretends to be Thing.
  ref( Wrapper->new( Thing->new ) )
    eq ref( Thing->new );

  package Thing;
  sub new { bless [], shift }

  package Wrapper;
  sub new {
      my ($class,$proxy) = @_;
      bless \ $proxy, $class;
  sub ref {
      my $self = shift @_;
      return $$self;


This module changes the behavior of the builtin function ref(). If ref() is called on an object that has requested an overloaded ref, the object's ->ref method will be called and its return value used instead.


To enable this feature for a class, use UNIVERSAL::ref in your class. Here is a sample proxy module.

  package Pirate;
  # Pirate pretends to be a Privateer
  use UNIVERSAL::ref;
  sub new { bless {}, shift }
  sub ref { return 'Privateer' }

Anywhere you call ref($obj) on a Pirate object, it will allow Pirate to lie and pretend to be something else.



A pragma for ref()-enabling your class. This adds the calling class name to a global list of ref()-enabled classes.

    package YourClass;
    use UNIVERSAL::ref;
    sub ref { ... }

A pragma for ref()-disabling your class. This removes the calling class name from a global list of ref()-enabled classes.


Currently UNIVERSAL::ref must be installed before any ref() calls that are to be affected.

I think ref() always occurs in an implicit scalar context. There is no accomodation for list context.

UNIVERSAL::ref probably shouldn't allow a module to lie to itself. Or should it?


ambrus for the excellent idea to overload defined() to allow Perl 5 to have Perl 6's "interesting values of undef."

chromatic for pointing out how utterly broken ref() is. This fix covers its biggest hole.


Joshua ben Jore -


The standard Artistic / GPL license most other perl code is typically using.