Is it possible to code a variable to be case sensitive?

For example I want x (lowercase) to be accepted as correct but X (uppercase) to be marked as wrong, without resorting to using a string. (so 1x or 1x would be accepted, 1X or 1X would not etc.)

I don’t actually mind which students use, but the way I coded an activity, CL reads them as separate variables, but accepts both as an answer, so when students mix and match its creates issues for dependent answers down the line. I never thought this would happen, but it did today…

Here is a simple example: