The URL you mentioned does redirect to https://supermarket.chef.io/cookbooks/cpan, which has no mention of Windows at all. Can you maybe tell us where the recipe(s) fail for you and how?

Yes I noticed that windows is not mentioned there - therfore the question, if windows-support is on the roadmap .... This is the error I have:

Compiling Cookbooks...
===========================================================0
Recipe Compile Error in C:\vagrant\cookbooks\windows\libraries\windows
+_privileged.rb
============================================================
LoadError
---------
cannot load such file -- windows/error
[download]

That's what in my recipe:

node[:Perlmodules].each do |modulename, moduleversion|
    cpan_client modulename do
        version moduleversion
        install_type 'cpan_module'
        action 'install'
    end
end
[download]

I'm aware that "user" and "group" are missing, but I don't know what to put there (esp. for "group".)

Be aware, I'm a Chef-Newbie

I don't know Chef and don't know much Ruby, but

Recipe Compile Error in C:\vagrant\cookbooks\windows\libraries\windows
+_privileged.rb
[download]

sounds as if the problem is in that file.