$x=\1;
$y=$$x;        # equivalent to $y = 1, i.e. a copy
$y++;
print $y;      #> 2

##</code><code>##

sub swap {
  my ($a, $b) = \(@_);
  
  ( $$a, $$b ) = ( $$b, $$a );  
 
  return;
}