We've had a discussion on #lua regarding the current documentation (or
lack thereof) of the 5.1 package model.
I've learned how the package model works simply by studying the
compat-5.1 module, but there is no guarantee that this
implementation is 100% true to the implementation in the lua core, and
the manual fails to deliver key aspects of how it works.
Most people only seem to touch the package model using require, module,
and package.path/cpath, and the whole aspect of loaders
seem to get lost, leading lots of people to regard overriding require()
as the only means of adjusting it's behavior.
So, I see it fit to provide additional documentation regarding this, and
also perhaps a page on the wiki which further explores it's uses.