parameter (list string);
return (list string);
storage unit;
code { CAR; NIL string; SWAP; PAIR; LEFT (list string);
       LOOP_LEFT { DUP; CAR; DIP{CDR};
                   IF_CONS { SWAP; DIP{CONS}; PAIR; LEFT (list string) }
                           { RIGHT (pair (list string) (list string)) }; };
       UNIT; SWAP; PAIR }