slash:~> perl -le 'print $^O' linux

As far as what modules are in what .debs, you should check out http://packages.debian.org. It lets you view lists of all of the packages in a specific (or all) releases of debian, view the files provided by a package, or search packages for words (or for specific files). For example, this is a search of what packages in 'stable' provide files named CGI.pm.