How to replace a character by an unprintable character ?

[jradix@bigfoot.com (J?r?me RADIX)]

Hello,

Using M-% or C-M-% how do you replace each `;' in

a;b;c;d

by a carriage return (<RET>) to obtain :

a
b
c
d

The FAQ is not very explicit on this :
http://www.gnu.org/software/emacs/emacs-faq.text
Question 5.9
It only tells how to *search* for unprintable characters but not how
to replace a character by an unprintable character.

Emacs info file is not clear on this either ( C-h C-k C-M-% )

I've tried several things out in the replacement string without
success :

\n
C-q <RET>
[\n]
$
?\n

none of them work.

If you have an idea...

Thanks,
Jérôme.