There's no example the author gives that contradicts it, but it's not quite RPN. In Lisp, the + operator is variadic -- it can take any number of arguments. So

There's no example the author gives that contradicts it, but it's not quite RPN. In Lisp, the + operator is variadic -- it can take any number of arguments. So in reverse-Lisp, this would be legal code: (3 4 2 +)