CPAN is about source distributions. not binary distributions. The only binaries you will find on CPAN are probably pictures (jpeg) and suchlike.

I think you are referring to C library interface modules. The bulk of the work (and code) takes place in C, either as source files in the distribution, or in third party libraries. There is some minimal Perl code inside the .pm, to "bootstrap" the shared library component.

To answer your question about pod in a binary distribution, this depends on your package manager. I have successfully used PAR in conjunction with a standalone Tk script that contains its own help text as pod (and I have a help function on the menu bar which displays the pod in its own window). I did have to jump through a few hoops, and I believe that it's easier to do in more recent versions of PAR and PAR::Packer.

I've given a talk on packaging Perl applications at two YAPC conferences, and I have submitted it to present at Houston TX in June.