[pptp-server] Format of /etc/ppp/chap-secrets

[Ivan Fetch]

Hello,
   I am writing a PERL utility to allow users to change their pptp
password in /etc/ppp/chap-secrets on their own.  I was wondering what can
(optionally) go in place of the *'s in a line like:
username * password *

Does anyone ever find reason to put other text (server and IP) in place of
the *'s?  IF so, can you give me some examples and such so I can
include such functionality into my script?

THanks,
Ivan.