To be fair, I hadn't even remotely thought of (i) the problem of logical drives being really part of the same physical drives, nor -more importantly- of (ii) plobsing++'s subtleties, assuming naively that a much simpler logic involving (something like) a %is_in_use hash holding arrayrefs of "transfers" (of which the first one to be considered active) would do. But eventually you're right that if I still roll up this enqueing utility/experiment of mine, then I may want to skip all the hassle and just enque everything at the user's request.