die "$writing_output ?" if $output_files{$writing_output}++;
my $tmp = "$writing_output.tmp";
open O, ">", $tmp or die "create $tmp: $!\n";
die "$writing_output ?" if $output_files{$writing_output}++;
my $tmp = "$writing_output.tmp";
open O, ">", $tmp or die "create $tmp: $!\n";