# @frame[0] = @frame[0] + @frame[1];
# @frame[1] = @frame[2];
# @frame[3] = @frame[2];

is better written as:

 $frame[0] += $frame[1];
 $frame[1] = $frame[2];
 $frame[3] = $frame[2];

You may notice that I also changed 

  @frame[0] = @frame[0] + @frame[1];

to

  $frame[0] += $frame[1];
  
just because it is shorter and nicer. 

 count($frame[0]);