I've come to prompt in this format and its working well for me. I once had your issue on another subject and it was indeed annoying.

"Claude - Im learning to program C - I wan't you to help me learn"

"I'm unsure what Im doing so can you walk me through the problem 1 step at a time? We can decide when to move to the next step but I want to be sure I understand each step as we go"

"Ok - I get it so far - Im ready for the next small step so we can discuss it"

You said: Can you write a C language regex, using regex.h, just to split the following structure on "=" or ";"

I mean, it did exactly PRECISELY what you asked it to do - you asked it to write a program and it did! Never mind anything, how cool is that??