use Benchmark;
$n = 1;   
timethese( 0, {
 'sub' => 'flipflop($n)',        
 'norm' => '$n = !($n)' } );

sub flipflop {
 $_[0] = !($_[0]) 
}

##</code><code>##

use Benchmark;
$n = 1;   
timethese( 0, {
 'sub' => '$n = flip($n)',
'norm' => '$n = !($n)' } );

sub flip { !($_[0]) }