my $num = 0xffff;
my $mask = 0xd0d0;
printf "
%b (0x%x) %d
&
%b (0x%x) %d
", $num,$num,$num,$mask,$mask,$mask;
print '-' x 31;

$num &= $mask;
printf "
%b (0x%x) %d", $num, $num, $num;

__DATA__
1111111111111111 (0xffff) 65535
&
1101000011010000 (0xd0d0) 53456
-------------------------------
1101000011010000 (0xd0d0) 53456