$pre = (shift) % 100;
$amble = (shift) % 100;
$post = (shift) % 100;	
if ($pre + $amble + $post != 100 ) {
	$pre = 100 - $amble 
           if ( $amble + $pre > 100 );
	$post =  100 - ($amble + $pre) 
           if ( $pre + $amble + $post != 100 );
}
print "$pre + $amble + $post = ", <br>
$pre + $amble + $post , "\n";