2 of 6 added 2 characters in body

><>, 46 43 + 3 for -v = 46 bytes

0&l?!v:f4*=?\l&:@+n$o!
00.  >&n;   >&:n1+$o

This is an implementation of xnor's algorithm in ><>.

It takes the input string on the stack (-v flag with the standard interpreter).

You can try it out on the online interpreter.