This is how I make the is () uppercase? block:
It is as simple as this. (if you are not working with lists, then you do not need the if () part). No reliance on Unicode codepoints. Just regular primitives, nothing sacred. It also works with foreign scripts like Greek, and safely handles characters that are not cased.
If you need the counterpart, is () lowercase?, just replace "upper case" in the dropdown with "lower case", and swap the ringed is () uppercase? with is () lowercase?.