my @LUHN10_map = ( 0, 2, 4, 6, 8, 1, 3, 5, 7, 9 );
sub johannz_LUHN10
{
	my @number = split('', shift);
	my ($sum, $pos) = (0, scalar(@number));
	$sum += $pos--%2 ? $_ : $LUHN10_map[$_]
		for (@number);
	($sum % 10 == 0) ? 1 : 0;
}