Ok, the DBD::MySQL problem that’s been vexing me for about a week is taken care of. I had to reinstall the entire MySQL system from binary packages to do it, but it all works now.
For you non-computer types out there, installing from binaries after trying to build a program from source is sort of the equivalent of having some engine trouble, trying to fix it yourself, and then buying a new car that looks almost exactly like your old one rather than dealing with the smoking heap of twisted wreckage that your inept wrenchwork created.