If you think that the operator in a Lisp form needs to be a function and if it were a function that it needs to return, then that's not the case in Lisp for pro

If you think that the operator in a Lisp form needs to be a function and if it were a function that it needs to return, then that's not the case in Lisp for probably 50+ years. Lisp is not generally following an eval/apply model and/or call/return model. (send foo :beep) This can mean: * SEND is a function, it's is called with the evaluated args, it may return or not * SEND is not a function and does something arbitrary Generally the model is: (operator ...) a) Where operator can be a special operator, something built-in, which is not a function. For example (throw 'foo "hello"), where THROW is a built-in special operator which transfers control. b) it could be a function, which is more like a procedure. The function could also do transfer control to some other place and never return, for example by calling THROW or by other operators which transfer control c) it could be a macro. The args don't need to be evaluated. Thus no eval/apply. The macro returns code, which gets executed. Again this could use other primitives, which transfer control. d) it could be a function itself like ((lambda (x y) ...) 13 14) What it needs: the first element in a Lisp form needs to be an operator, which is usually a symbol with some meaning: special operator, function, macro. Scheme then in the mid 70s added that the first element is evaluated and can be a general variable. Thus in Common Lisp: (let ((actor (create-actor :name 'foo))) (send-async actor :init)) could be written in Scheme (let ((actor (create-actor 'foo))) (actor :init)) given that the actor would be a function object. > my-actor async messge_args Writing it as (send my-actor :async message-args) Is basically just a syntactic transformation. The semantics could be the same. If we want write (my-actor async message-args) then one would typically a) switch to a model like in Scheme, where the actor would be a function object or b) write a translator for a new language to ordinary Lisp or c) write a new evaluator for that