use strict;
use threads;
use Thread::Queue;

my $PingQueue    = Thread::Queue->new; 
my $PingResQueue = Thread::Queue->new;
my $requestsinprocess = 0;

my $ping = 'ping -c 1';                                  # Ping for Linux
$ping = 'ping -n 1' if ( $^O eq 'MSWin32');              # Ping for Windows

foreach my $i ( 0..7 ) {                                 # Create some threads
  my $pingthread = threads->new(\&Ping,$i)->detach;
}

  while ( 1 ) {
    # Check for finished pings
    if ( $requestsinprocess > 0 ) {                                    # Check if there is anything on PingResQueue
      while ( defined ( my $pingres = $PingResQueue->dequeue_nb ) ) {  # with a non blocking dequeue of PingResQueue
        print "$pingres\n";
        $requestsinprocess--;
      }
    }

    if ( $requestsinprocess == 0 ) {              # Start a new round with pings
      foreach ( 0..17 ) {
        $PingQueue->enqueue("127.0.0.1");         # Put ip on PingQueue, it's dequeued in &Ping()
        $requestsinprocess++;
      }
    }

    select( undef, undef, undef, 0.1 );           # Sleep a while
  }

exit 0;

sub Ping {
  my $id = shift;
  my $tolalping = 0;
  while (my $ip = $PingQueue->dequeue) {            # Block here and wait for an ip on PingQueue
    my $pingres = `$ping $ip`;                      # Do a system call
    $PingResQueue->enqueue("$id " . $tolalping++);  # Put something on PingResQueue to be dequed in the main thread
  }
}