Writing good comments is at least as hard as writing good code. Bad comments can be worse than bad code. Comments can give the reader the impression that they understand the code without the need to actually read and understand the code. If the comments are good, that's fine. If the comments are bad that can lead to a great deal of wasted time and frustration.

Don't get me wrong. Comments are an important part of writing good code. But it is better to write good code that speaks for itself than to write a translation of the code into some semblance of English (or whatever language is appropriate).

Good comments convey the intent of code and may explain how a tricky algorithm works, but doesn't give a blow by blow description of the code.

Modules provided by CPAN are written by people of vastly varying ability and can demonstrate code on many different levels, but few of those modules are written for their educative value. "Dumbing down" a module so that it is accessible to learners doesn't help CPAN and doesn't actually help learners. For one thing, there are much better ways to learn Perl basics (PerlMonks for a start), and for another: learners don't stay learners for ever, so what level should the comments and code be aimed at?

Comments in code for CPAN should be designed to ease the job of maintenance programmers. Generally that means few comments and much thought given to appropriate coding, identifiers, documentation and test suites.

That is not to say either that there isn't a lot to be learned from reading CPAN code. There is a great deal that can be learned from examining CPAN code. But you shouldn't expect it to be entry level stuff.