#! perl -slw
use strict;
use threads;
use threads::shared;
use Thread::Queue;

our $MAX //= 10;

my $sem: shared;
my $Q = new Thread::Queue;

sub thread {
    while( my $printme = $Q->dequeue ) {
        lock $sem;
        print $printme;
    }
}

my @threads = map async( \&thread ), 1 .. $MAX;

my $array = 'list.txt';
open my $handle, '<', $array;
chomp, $Q->enqueue( $_ ) while defined( $_ = <$handle> );
close $handle;

$Q->enqueue( (undef) x $MAX );
$_->join for @threads;