Ability to identify undeclared variables in my test steps before running the test

Some times we have variables used inside xpath of locators or in the functions and db queries and we may not remember when copy and paste them in a new tests and if we haven't declared them before the steps, the test will run until some where the compare doesn't match. It would be very helpful if PROOF identify the steps that have undeclared variables on them so we can declare them in beginning steps.