Saving stuff in the session?

I have a couple of web pages that are being installed as an extension
(along with Scrips and Actions etc). I want to pass information from one
part of the web interface to another part of the web interface. I thought
of using the session, having the mason code setting $session{‘Clients’} =
“testing” and retrieving it in another mason file using
$RT::Logger->debug($session{‘Clients’});, but it always giving me the error
“Use of uninitialized value $HTML::Mason::Commands::session{“Clients”}” in
my log file. Is there another way of storing things in the session?