$a=$a ^ $b;
$b=$a ^ $b;
$a=$a ^ $b;
$b=$b ^ $c;
$c=$b ^ $c;
$b=$b ^ $c;

##</code><code>##

  $b=$b^$c;
  $a=$a^$c;
  $c=$a^$c;
  $a=$a^$b;
  $a=$a^$c;
  $b=$a^$b;