o conf makepl_arg --perl_only

Seems to do the job, I was trying something like:

o conf makepl_arg PREFIX=--perl_only

But that didn't work.

Argh! The problem is, I'm already passing something like this to the CPAN shell:

o conf makepl_arg LIB=/path/to/my/distros/perllib

When you set the "--perl_only" paramater, it erases the "LIB=" paramater.

I guess I have to figure out how to pass both configuration thingies.