[luatex] Loading Lua modules

[puppi ;]

I'm very new to LuaTex, but a reasonably experienced Lua programmer. The
major drawback I face in using LuaTex for any practical purposes is the lack
of support for loading regular Lua modules, in the usual way. I can't see
why the devs didn't preserve the usual entries in package.loaders, just
pushing them a few indices forth. Does anyone know a (practical, preferably
portable) workaround?