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

$|++;
our $THREADS ||= 10;

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

sub worker {
    while( my $url = $Q->dequeue ) {
        chomp( $url );
        { lock $sem; print "fetching $url" }
        my $content = get "http://$url/";
        lock $sem; 
        print "$url : ", $content && $content =~ /ok/ ? 'ack' : 'nack' 
    }
}

$Q->enqueue( <> );
$Q->enqueue( (undef) x $THREADS );

my @threads = map threads->create( \&worker ), 1 .. $THREADS;

$_->join for @threads
__END__

C:\test>715836 urls.txt
fetching www.bbc.co.uk
fetching news.bbc.co.uk
fetching www.ibm.com
fetching www.yahoo.com
fetching www.microsoft.com
fetching www.google.com
fetching www.google.co.uk
fetching www.google.co.au
fetching www.cnn.com
fetching www.msnbc.com
www.google.co.au : nack
fetching www.perl.org
www.google.co.uk : ack
fetching www.nasa.com
www.yahoo.com : nack
fetching www.ask.com
www.google.com : ack
fetching www.itv.com
www.perl.org : nack
www.nasa.com : nack
www.ask.com : nack
www.msnbc.com : ack
www.itv.com : nack
www.ibm.com : ack
www.microsoft.com : ack
news.bbc.co.uk : ack
www.cnn.com : ack
www.bbc.co.uk : ack