######Semaphore implementation #####

use IPC::Semaphore
sub IPC_PRIVATE {0};
sub IPC_RMID    {10};
sub IPC_CREAT   {0001000};
sub GETVAL      {5};


sub semwait {
    my $sem=shift;
    semop($sem, pack("s3", 0, -1, 0)) || die "semw: $!\n";
}

sub semsign {
    my $sem=shift;
    semop($sem, pack("s3", 0, +1, 0)) || die "sems: $!\n";
}

my $sem=semget(&IPC_PRIVATE, 1, &IPC_CREAT | 0666) || die "semget: $!\n";
warn "semid= $sem\n";
semsign($sem);


####### Pipes implementation ########

use IO::Handle;
pipe(PARENT_READ, PARENT_WRITE);
PARENT_WRITE->autoflush(1);

#### In the child process #####

{
   semwait($sem);
   print PARENT_WRITE "PID : Pid of the process is $$ \n" ;
   print PARENT_WRITE "SIGNAL : Signal sent from the process \n";
   semsign($sem);

}

##### In the parent ##### 
{
  while ( $msg = <PARENT_READ> && $signal_received < $total_signals )
   {
     if($msg =~ /PID/)
     {
      chomp($msg);
      my @fields = split (/ /,$msg);
      print "Child with fields @fields has communicated to me \n";
     ##### This print statement is not printing anything either on the console or even if I redirect it to a file 
     }
   } 
}