Write Roman Numeral literals in Common Lisp using the with-roman macro. This will introduce a binding for all literals used within the body forms.
Example usage at the REPL:
CL-USER> (ql:quickload "cl-roman")
CL-USER> (cl-roman:with-roman (print (- (+ M M) III)))
MCMXCVII
1997 (11 bits, #x7CD)
CL-USER> (cl-roman:with-roman (eq (* X X) C))
T