iRule to log Proactive BotDefense to HSL?

We are running v12 LTM/ASM and have observed active botnet attacks. We enabled Proactive BotDefense; however as we found out from support tonight logging is not available until version 13.x. In reading other posts there is a way to log events via iRule. Has anyone successfully got this to work in version 12? We are very close to upgrading, but won't make in time with this event going on in the background. Any insight or samples are greatly appreciated!

/jeff