Very cool! But you can save the double lookup easily:

sub FETCH { 
 
  my($self, $key) = @_; 
 
  unless (exists $self->{$key}) { 
    if (my $meth = $self->can($key)) { 
      $self->{$key} = $meth->($self);
    } 
    else { 
      warn "No method for '$key'"; 
      $self->{$key} = undef; 
    } 
  } 
  return $self->{$key}; 
}
[download]

That's because $obj->can('meth') returns the coderef to execute!

-- Randal L. Schwartz, Perl hacker