is --Operation (predicate), two inputs.
     The inputs can be any Logo objects. The output is the word true if
     the two inputs are identical. That is, they must be of the same type
     (both words or both lists), they must have the same count, and their
     members (if lists) or their characters (if words) must be identical.
     The output is the word false otherwise. (Note: this is an exception
     to the convention that names of predicates end with the letter "p".)