The examples you should be following are the ones in Apache::Session and in eg/example.perl. Just take that and replace the tie() call with the appropriate parameters for Apache::Session::MySQL, which looks like what you have now.

You are missing something about the core structure of Apache::Session. It's a toolkit of storage, locking, and ID generation modules. The Apache::Session::MySQL module is just a pre-set configuration of those. It's little more than a config file. Look at the source and you'll see what I mean.

If you want to choose a specific ID generation algorithm, you can't use Apache::Session::MySQL because it already has one selected. You have to use Apache::Session::Flex instead. However, the MD5 ID generator which you are trying to use is already the default for Apache::Session::MySQL, so you don't need to do anything.