Your question is somewhat unclear to me.

I assume that you are looking for documentation for the Perl modules you get from CPAN or somewhere else. Perl modules normally include their documentation right in the source code in the POD (Plain Old Documentation) format, and different outputs are generated when you install the module. Under UNIX, perldoc modulename will show you the documentation and with ActiveState Perl under Windows, the documentation will be included with the HTML documentation for ActiveState Perl itself.

If you look for documentation beyond what's included and / or automatically generated, there are not many possibilities. Some of the Books about Perl discuss several important modules like CGI.pm, at other times, the module author might be of assistance, but in general, Perl modules lack good documentation, as it is the case with most open source stuff. Of course, the Open Source Apology for not providing documentation also holds here, you can still look at the module source code to figure out how it works :).

A special case is the Image::Magick module, where the documentation is not included with the Perl modules (but only a meagre page telling us it has more bugs than the imagemagick program suite alone), but the Perl documentation comes with the ImageMagick program suite itself (for reasons unknown to me).

Of course, if you have any specific questions or are in search of examples, a question here will most likely turn up many useful answers.