A few months back, I was able to get some proof of concept code working. See my thread, especially the summary code in this post. I don't know whether the things I learned in that set of experiments will help, but I was able to make use of the @dmvar user-defined variable; I don't think it had to be inside of the DebugMe mySQL function to work... that's just specifically what I was trying to get at for that one. But I thus know that user-defined variables aren't out of the question in DBD::mysql.

(caveat: not an SQL or mySQL expert)