#Open the output file for saving the results;  
  open my $fh_out, '>', $write_dir.'/'.$filename
      or die "failed to open '$filename' for write";

##</code><code>##

  my $full_filename = $write_dir.'/'.$filename;
  open my $fh_out, '>', $full_filename 
      or die "failed to open $full_filename for write $!";