#! perl -slw
use threads;
use threads::shared;
use LWP::UserAgent;
use HTTP::Request;

my $semStdout :shared;
my $running :shared = 0;
open(LIST,"urls.txt");
while ( my $tld = <LIST> ) {
    chomp $tld;
    Win32::Sleep( 100 ) while do{ lock $running; $running >= 10 };
    async{
        { lock $running; ++$running; }
        my $url = "http://$tld/";

        my $ua = new LWP::UserAgent;
        $ua->timeout(5);
        $ua->agent("Mozilla/6.0");

        my $req = HTTP::Request->new('GET',$url);
        my $res = $ua->request($req);
        my $content = $res->content;
        my $status = $content =~ /OK/i ? 'ack' : 'nak';
        {
            lock $semStdout;
            printf "(%3d)$tld: %s\n", threads->self->tid, $status;
        }
        { lock $running; --$running; }
    }->detach;
}
close(LIST);