Strange kata. It is not clear what is needed in the case of tests "2 3" or "2c4". Throwing an exception and continue working - error. And what you need?

"Referencing a non-existent variable will cause the interpreter to throw an error. The interpreter should be able to continue accepting input even after throwing." What about the other exceptions? What text and what to display?

It is impossible to understand: what is the expression format? (,), +, -, *, / are they all separated by spaces, as in the task description? Or can it occur without spaces, as written in the comments?
It is impossible to solve a problem without understanding its conditions.

Unfortunately, I did not understand at all what the task was about. Separately, everything is clear, but not all together.

This is a way to arounding up to nearest integer. For example 3/2 mast be 2, not 1.