use MCE;
use MCE::Candy;

my $iterator = get_dir_file_list_iter($dir);
open my $fh_out, ">, $ fn_out;
my $mce = MCE->new(
    gather      => MCE::Candy::out_iter_fh($fh_out),
    chunk_size  => $iter_file_ct,
    max_workers => $max_workers,
    user_func   => \&parse_files,
)->spawn;
$mce->process($iterator);
$mce->shutdown()
);