use strict;
use warnings;
use threads;
use MCE::Shared;

mce_open my $err_fh, '>>', \*STDERR;

sub task {
    my $id = shift;
    my $str = "ab " x 3000;
    for (1..10000) {
        print $err_fh $str, "\n";
    }
}

threads->create('task', $_) for 1..40;
$_->join for threads->list;