RLM_Perl Question

Hi All, This is probably a rather easy one and I am certainly overlooking something simple somewhere. I trying to write out if the request was accepted or rejected using RLM perl into a json file. I am able to get everything under the sun for the request apart from this simple thing. Looking at how this is done in the sql module it appears its just a simple expansion of %{reply:Packet-Type}, but cant find a way to do the same in RLM perl. Thanks in advance. Many Thanks Arnab