[parenscript-devel] Need a meaningful error message when PS macro references unbound var

When a macroexpansion tries to evaluate an unbound variable, as in the following, (ps (macrolet ((blah () x)) (blah))) the resulting error message is unhelpful: "Attempt to take the car of "Unbound Value" which is not listp." Could it say "Attempt to take the value of the unbound variable X" instead? Daniel