Search the set of local or global variables for the one with
the name contained in Result.
If the search is successful, place
the value of the variable into Result.
Then do action 5.
If the search is not successful, trap execution.
If Nameind is True, trap execution.
Otherwise, do action 5.
Apply the unary operators in A (if any) to the value in
Result, in a right-to-left order.
Place the result of this application into Result.
A.