ELisp Interactive Calls

[mflynn]

After all these years I'm trying to teach myself how to write Emacs Lisp 
programs.

To call this function:

(defun my-test-function (arg1)
  "DOC: Multiply two numbers."
  (interactive "p")
  (message "The square of the arg is: %d" (* arg1 arg1))
)


I type:
Ctrl-U 8 Esc-x my-test-function

and 64 is printed, as I would expect.

But I'm not sure how to supply two args interactively.

(defun my-test-function (arg1 arg2)
  "DOC: Multiply two numbers."
  (interactive "p p")
  (message "The product of the args is: %d" (* arg1 arg2))
)

How do I call this?  If I type Ctrl-U 8 8 Esc-x my-test-function

the call fails with a Wrong number of args message.   The second 8 I type just 
shows up in the scratch buffer.

Thanks