There is a huge advantage to "pushing out the whole distribution": You know that what it is on the production servers is exactly what you tested on the reference/staging servers.

That said, a much easier way to accomplish a "just the new stuff" update would be to use rsync, which is a tool for making the files at the destination the same as the source. rsync will do all the dirty work for you.

Otherwise, if you are customizing modules you got from CPAN, download the tar file from CPAN, extract, apply your changes to the freshly extracted package, run the tests, then install and do more testing. If everything works correctly, then you can repackage it. Read perlnewmod and related documents to learn more.

Updated: Fixed a typo.