Two notes:

1. Your pipe is on the wrong side. It should be:

   open(P,'./from.pl|');
   while (<P>) {
      print;
      $count++;
   }
   close(P);
   print "$count\n";
   [download]

   which gives you what you expect.
2. Make sure your scripts are mode +x! If you can't run them from the command line, they won't work.

In general, though, remember - put the pipe on the side as you would if you ran them on the command line; that is: ./from.pl | ./piper.pl would be what you'd run in this case, so use the pipe after the script name. (If you wanted to write to it, you'd put the pipe before.)