Been using perl on and off for a while but on a rainy afternoon started looking at OO. Normally with I can figure out all problems by reading other people's posts but I don't seem to be getting anywhere with this one, despite it being REALLY BASIC! Your forgiveness in advance is required. 
#!/usr/bin/perl

use strict;

Cow->speak;

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

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

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I copied this directly from http://perldoc.perl.org/perlboot.html. When I run it I get 
Can't locate object method "speak" via package "Cow" 
at ./testOO1.pl line 6.

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In fact I can't seem to get inheritance to work at all. What extremely silly thing am I (not) doing? Thanks

In reply to really simple OO inheritance question by tomgracey

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