foreach my $shuffle_id (1..$permutation) {
    my $pm     = Parallel::ForkManager->new( $multi_cpu_num );
    PFM:
    for my $pwm (@ciona_pwm_array) {
        $pm->start and next PFM;
        count_pwm_num($pwm,$seq_1,$seq_2);
        $pm->finish;
    }

    $pm->wait_all_children;
}