[racket] Call racket with long code from racket

> You could try something like this:
> #lang racket
> (require racket/system)
> (display (port->string (car (process (format "racket -e '~a' " '(+ 2 3))))))

That does not work in the following case

 (display (port->string (car (process    (format  "racket -e \" ~a \" "
                                                "
                                                (require mzlib/defmacro)
                                                (define-macro (my-when
test . body)`(if ,test (begin , at body) '() ))
                                 (my-when #t '(5 6 7))
                                                "
                                                )))))