Put your sessions on a fast disk. Your operating system and/or filesystem cache and/or hard disk cache will optimise this away to never touching your hard disk.

I insert another layer. Using CGI::Session::DB2, I have the hard disk cache, the filesystem cache, the database cache, and probably something else I'm missing, all pretty much keeping me safe. ;-)

Also, I'm not even sure that CGI::Session will save anything if the session is deleted immediately like this - it should save during the destruction of the object, where you've already marked it for deletion. So, even though the above says that your physical disk is never touched, this says it likely isn't even asked.