package Action;

sub new {
  my ($class, %args) = @_;
  my $coderef = sub { while (my ($k, $v) = each(%args)) { ... } };
  return bless($coderef, $class);
}

sub foo {
  $_[0]->();
}

##</code><code>##

package SingletonObject;
{
  my $instance;

  sub instance
    {
      unless (defined $instance) {
        $instance = bless ({}, $class);
        # other initialization stuff
    }
    return $instance;
  }
}