We'd like to thank the good folks at UserActive. Their great tutorials have helped in many areas. Here you can read all the clues. There is a very specific way of doing that. It's like a magic incantation.
Meaning just do it until it makes sense.
It means take whatever is mentioned next and do the opposite. You will find that these will match any lowercase letter in the first case and matches any lower OR upper case letter in the second case. But don't take our word for it. That would be wrong.