bundling multiple modules with Module::Build

I couldn't figure this out from the docs.  I haven't found a way with
MakeMaker, and would prefer to use M::B anyhow.

My distro is very simple currently:

Lingua::Slavic::Numbers contains:

Lingua::Slavic::Numbers
Lingua::BG::Numbers (requires Lingua::Slavic::Numbers but does not use inheritance)
(plus other Lingua::LL::Numbers for LL in (RU SR etc.))

Tests in t/ exercise both modules listed above.

How to I write the build file for this?  All the examples show how to do
it for one top module but I have two.

I can't rename Lingua::BG::Numbers because CPAN has a convention for
that name format.

Thanks
Ted