package Printable;
  
  sub print_on {
    my $self = shift;
    my($fh)  = @_;
    print $fh $self->as_string;
  }

  sub as_string { $_[0]->value }

  sub new {
    my $proto = shift;
    my $scalar;
    my $self = bless \$scalar, ref($proto) || $proto;
  }

  sub set_value { 
    my $self = shift;
    $$self = $_[0];
    return $self;
  }

  sub value { ${$_[0]} }

  sub print { $_[0]->print_on(\*STDOUT) }

  package Decorator;
  use base 'Printable';
  
  sub decorate {
    my $proto = shift;
    my($target) = @_;

    $self->new->set_target($target);
  }

  sub new {
    my $proto = shift;
    my $self = bless {}, ref($proto) || $proto;
    $self->init;
    return $self;
  }

  sub init { }

  package MultiString;
  use base 'Decorator';

  sub count {
    my $self = shift;
    exists($self->{count}) ? $self->{count} : 1;
  }
  
  sub set_count {
    my $self = shift;
    $self->{count} = $_[0];
    return $self;
  }

  sub as_string {
    my $self = shift;
    $self->target->as_string x $self->count;
  }

  package FormatBold;
  use base 'Decorator';

  sub as_string {
    my $self = shift;
    '<b>' . $self->target->as_string . '</b>';
  }

  package main;

  $thing = 
    MultiString->decorate(
      FormatBold->decorate(
        Printable->new->set_value("Hello, world");
      )
    )->set_count(5);

  $thing->print;