Checking if all referenced variables exist?

[kinsi55]

If I have a case where the expression is always evaluated against an object containing a specific list of variables, what would be the intended way to sanitize the passed expression? I assumed I could use variables() in one way or another, however that will also return variables which are defined in the expression itself.

I have a hacky solution now where I recursively iterate over the tokens and account for every IVARNAME this way but surely there has to be a better way for this right?