I bet searching here on monks would have given you a few examples of how monks do this. There is a plethora of scripts available by now as there are many ways to answer the question.

I also wrote a script myself, but with a few additions to make it easier to find module not (yet) installed, so that I don't have to dig on CPAN when I'm looking for a module that does XML/XPM/CSV/mysql/...

Note that my script works based on the list of modules available as seen by CPAN, so it will not find modules that were manually copied into the perl tree.

$ modlist -?
usage: modlist [ -a AUT ] [ -r ] [ -i ] [ -nc ] [ <pattern> ]
        -a | --author=AUTHOR_ID  Only modules from author
        -r | --registered        Only registered modules
        -i | --installed         Only installed modules
        -n | --new               Only new modules
        -c | --csv               Output module and version as CSV
        <pattern>                Only modules that match pattern
$ modlist -i xpm
Module name               Description                                 
+ Version
Bundle::Image::Info::XPM                                              
+     0.01
Image::Info::XPM                                                      
+     1.07
Image::Xpm                                                            
+     1.12
Tk::XPMs                                                              
+     1.11
$ modlist -r peek
Module name               Description                                 
+ Version
Apache::Peek              Devel::Peek for mod_perl
Data::Peek                A collection of low-level debug facilities  
+     0.31
Devel::Peek               Peek at internal representation of Perl data
+     1.04
                          Core since    5.006 1.00_01      in 5.010001
+     1.04
POE::API::Peek            Peek into the internals of a running POE env
$
[download]

It also does colorizing (when available), shows if it is a CORE module (using Module::Corelist), since when and what version in core,