I'm going through merlyn's OO tuturial. I'm getting a Can't locate object method "speak" via package "Cow" error on the following bit of code:

#!/usr/bin/perl

my @pasture;
my $animal;

    @pasture = qw(Cow Cow Horse Sheep Sheep Cow);
    foreach $animal (@pasture) {
      $animal->speak;
    }


{ package Cow;
    @ISA  = qw(Animal);
    sub sound { "moooo" }
}

{ package Horse;
    sub sound { "neigh" }
    sub speak {
        my $class = shift;
        print "a $class goes ", $class->sound, "!\n";
    }
}

{ package Sheep;
    sub sound { "baaaaaaaa" }
    sub speak {
        my $class = shift;
        print "a $class goes ", $class->sound, "!\n";
    }
}

    { package Animal;
      sub speak {
    my $class = shift;
    print "a $class goes ", $class->sound, "!\n"
      }
    }
[download]

$PM = "Perl Monk's";
$MCF = "Most Clueless Friar";
$nysus = $PM . $MCF;