{ package Animal;
      sub speak {
        my $class = shift;
        print "a $class goes ", $class->sound, "!\n"
      }
    }
    # Animal package from before
    { package Mouse;
      @ISA = qw(Animal);
      sub sound { "squeak" }
      sub speak {
        my $class = shift;
        print "a $class goes ", $class->sound, "!\n";
        print "[but you can barely hear it!]\n";
      }
    }

    Mouse->speak;

##</code><code>##

    a Mouse goes squeak!
    [but you can barely hear it!]