I didn't find an easy way to take an existing IRC client and just swap out its connection routine.
Your two approaches would be to either use an existing client and find out how to make its socket connection speak SSL. For example the connect method in AnyEvent::IRC::Connection should be all that's needed to make AnyEvent::IRC speak SSL.
The other approach would be to write your own irc client, using for example Parse::IRC. If you go this route, swapping out the transport layer is even easier, at the cost of actually having to implement an IRC client.