CHAP with perl module

["Jeremy Kusnetz" <jeremyak@gmail.com>]

From RFC: 2865:

The random challenge can either be included in the
   CHAP-Challenge attribute or, if it is 16 octets long, it can be
   placed in the Request Authenticator field of the Access-Request

   packet.

We are able to retrieve the clear text password and encrypt it with the CHAP-Challenge and see if it matches the CHAP-Password,
but as far as I can tell, we don't have access to the Request Authenticator of the Access-Request packet in the perl module.

Any thoughts on how to support the RFC?