sub union_of_h1_h2 {
  my ($h1_ref, $h2_ref) = @_;
  my %output = %$h1_ref;
   
  for my $topkey (keys %{$h2_ref}) {
    for my $filename (keys %{$h2_ref{$topkey}}) {
      for my $bottomkey (keys %{$h2_ref{$topkey}{$filename}}) {
     	  $output{$topkey}{$filename}{$bottomkey} = $h2_ref->{$topkey}{$filename}{$bottomkey} unless (Condition);
      }
    }
  }
  return \%output;
}