# Takes a list of comparison subroutines for a sort, and
# returns a combined comparison subroutine.
sub combine_comp_subs {
  my @subs = @_;
  if (1 == @subs) {
    return shift @subs;
  }
  else {
    return sub {
      foreach my $sub (@subs) {
        my $c = $sub->();
        return $c if $c;
      }
      return 0;
    };
  }
}