Arithmetic in Functions

In a tag I have artist - title. I want to extract title. Using len - strstr in the function doesn't work, the arithmetic is ignored.
How do I do this?

EDIT: Got it. Use sub()

Well, it should. So please show us the expression and the data.

On the other hand: it may be easier to use an action of the type "Guess value" (import tag field) for %artist%
Pattern: %artist% - %title%

I got it - use $sub(x,y)