{
  my (%handles, %did_mkdir);
  sub get_out_file {
    my ($make, $model) = @_;
    if (!defined $handles{$make}{$model}) {
      if (! $did_mkdir{$make} && ! -d "$out_dir/$make") {
        system "mkdir -p $out_dir/$make";
        $did_mkdir{$make} = 1;
      }
      open $handles{$make}{$model}, "$out_dir/$make/$model" or die $!;
    }
    return $handles{$make}{$model};
  }
}