Invalid expression result

Synopsis
You specified an invalid expression.

Cause
An add-on library, Exit handler, or Environment was passed a expression by your script, but that expression is not valid.

Cure
Consult the documentation for that product to see what arguments you should be passing to a particular function/command that you're trying to use in that add-on library, Exit handler, or Environment. Look up this error message in that documentation. Check that you have the latest version of the software.