use strict;
use threads;

open my $fh, '>', 'outfile' or die $!;
my $th = 0;
my @threads = map {
    $th++;
    async( sub { sleep(1); for(1 .. 30_000) { print $fh "Thread $th\n" } } );
} (1 .. 500);
$_->join foreach @threads;
close $fh;