#!/usr/local/bin/perl -w

use strict;

{
   test ('arf', undef, 'dog');
}

sub test
{
   @_ == 3 or die "Incorrect number of arguments";

   my ($a, $b, $c) = @_;

   my %hash = ('arf' => {'spot' => {'dog' => 3}});

   print $hash {$a}->{$b}->{$c};
}