I would like to press enter in my Elisp script when I am in a REPL window.
but (newline) just moves the cursor to the next line and not simulate the press of the Enter key on my keyboard.
Is there a function in Emacs Lisp that works in Emacs interactive mode?
In Emacs, depending on the mode you are, the same key may have different definitions (that is, it may be bound to different commands). The best way to simulate a key press is to get exactly which function is bound to that key. You can do that with lookup-key. This function will return a function that is bound to whatever key you look up. To execute the function, use funcall:
(funcall (lookup-key (current-local-map) (kbd "RET")))
The function current-local-map returns the key map for whatever context you are in. You can use other maps depending on what you want, such as current-global-map.