use threads;
use threads::shared;
use Thread::Semaphore;
use IO::Handle;
use strict;

my $sem = Thread::Semaphore->new();
my $seq  :shared = 1;

my $th1 = threads->create('Printer', $ARGV[0]);
my $th2 = threads->create('Printer', $ARGV[1]);

$th1->join();
$th2->join();

sub Printer {

   my $f = new IO::Handle;
   my $fn = shift;
   my $ifh;

   print "The filename is: $fn\n";

   if (open ($ifh, '<', $fn) == 0 ) {
      my $tid = threads->tid();
      print "\n\nError: problem opening up file: $fn. Exiting threads: $tid\n";
    
      return 1;
   }

   my $msg = "";

   if ($f->fdopen(fileno($ifh),"r")) {
      print "successfully opened up .\n";
   } else {
      print "\n\nError opening up input file.\n";
      return 2;
   }

   while (defined($msg = $f->getline())) {

      $sem->down();
   
      $msg = "<$seq>: " . "$msg";
      print "message is: $msg\n";
      $seq++;
      $sem->up();
   
   }
   $f->close();
}