I tried to learn Perl by reading module code once and learned (the hard way) that is is not a very a good idea for several reasons:

• Some of the code in CPAN modules is actually not good and should not be emulated. Core modules are very good, but can be sparsely documented. Finding a good module that is clearly written and well documented would be a good idea, but read on...
• There are LOTS of modules, many of which are very intersting and have awesome techniques that I found fascinating at the time but I have rarely (if ever) actually used.

One of the links you added has the following quote that encapsulates what I feel is a much better approach: "The best way to learn anything, Perl included, is to use it for useful work. If you don't have a task that needs doing, you aren't going to do it, but if it needs doing, then you will be motivated to do it."

I think that quote pretty much speaks for itself. Also, don't forget that writing up responses and trying to solve the problems of other Perlmonks is a good way to help hone your skills. You may find that you thought you had a pretty good answer to an issue only to find that your solution was exceedingly verbose, stupid (it has happened to me a few times), or was simply inferior to someone else's. You learn by trying and developing a slightly thick skin. You will need it anyway.