Thanks. While I digest this suggestion, here's the big picture as requested.
I download podcasts from a number of sources. Each feed has its own peculiarities, requiring feed-specific coding, which I wish to isolate as modules. On the other hand, local processing is not feed-specific.
% download_processor feed1
% download_processor feed2
% ....
and there are modules feed1.pm, feed2.pm, and so on. What I would like to accomplish is when a new feed comes along, I just write a module for the new feed and don't have to modify the download_processor.