my $str = "1010101011";
my $second = "0$str";
my $xor = $str ^ $second;
my $result = $xor | "0" x length $xor;

##</code><code>##

my $mask = "0" x length $result;
substr($mask, $_, 1) = "1" foreach 2, 5, 8;
print "It passes!" if ($mask & $result) eq $mask;