sub sort_fun
  {
    # Get a has ref and and sort spec
    my($hash_ref,$sort) = @_;

    my @sort_columns = split(/[\|\,\+]/,$sort);

    # Do some stuff...

    # Create a closure function
    return sub 
      {
        # Test stuff...

        foreach my $col (@sort_columns)
          {
            # lexically() is like an extended version of cmp
            my $ret = lexically($hash_ref->{$a}->{$col},
                                $hash_ref->{$b}->{$col});
            return $ret if($ret != 0);
          }
        return 0;
      }
  }


my $sort_fun = sort_fun(\%tracks,"year|name");
foreach my $id (sort $sort_fun keys(%tracks))
  {
    # Do something for every $id
  }