Gnus-Pers (personalities)

[Hadron Quark]

I tried to set up .gnus.el posting-styles with no success : so now I try
Gnu-Pers instead (http://www.emacswiki.org/cgi-bin/emacs-en/GnusPers).

Can some one please who me how they have configured a rule to match a
personality to a regular expression

e.g

I want to use personality "xxx" when I am in newsgroup, for example,
"comp.sys.ibm.pc.rpg" and press "a". From the scanty documentation it
seemed that I must check for "*.rpg" against symbol "group" but I'm
really not too sure anymore.

I used "customize-group, personalities" and have 3 personalities set up
which I can successfuly select using "gnus-presonality-choose" (C-c
C-p). I have a default personality, but I really cant see how to match a
newsgroup name and then select a non default personality.

Any pointers greatly appreciated : I'm sure its something obvious that
I'm blind to.