use strict;
use threads;
use threads::shared;
use Thread::Queue;
use Net::Ping;

use constant NUMBER_OF_THREADS => 20;
use constant TIMEOUT => 4;
use constant INPUT_FILE_NAME => "slist.txt";

our %results : shared;

sub pingworker
   {
   my ($Qin, $timeout) = @_;
   my $response;
   while (my $server = $Qin->dequeue)
      {
      $response = Net::Ping->new()->ping($server);
      lock(%results);
      $results{$server} = $response ? "Alive" : "Timed Out";
      }
   }
 
my $Qwork = Thread::Queue->new;

my $thread;
for (1 .. NUMBER_OF_THREADS)
   {
   $thread = threads->new(\&pingworker, $Qwork, TIMEOUT);
   $thread->detach;
   }

open(SLIST, INPUT_FILE_NAME) || die "Cannot open server list: $!\n";
while (<SLIST>)
   {
   chomp;
   $Qwork->enqueue($_) if /[A-Za-z0-9\.\-_]+/;
   sleep 0.5 while $Qwork->pending > NUMBER_OF_THREADS;
   }
close(SLIST);

$Qwork->enqueue( (undef) x NUMBER_OF_THREADS);

sleep 0.5 while $Qwork->pending > 0;

foreach my $server (sort keys %results)
   {
   print $server . "," . $results{$server} . "\n";
   }