Perl for Windows
Perl for Windows supports most of the core set of Unix features, as well as a number of extensions for Win32 features. If you've installed the ActiveState version of Perl for Windows, you'll get the Win32 modules as part of that package. If you compile Perl for Windows yourself, you'll need to get the libwin32 package yourself from CPAN (see http://www.perl.com/CPAN-local/modules/by-module/Win32/ for the latest version). Otherwise, the functionality is the same.
Earlier versions of Perl for Windows were much less coordinated as far as which modules and features were available in which package. If you're using a version of Perl earlier than 5.6.1 (or ActiveState's Perl earlier than Build 631), you should upgrade to make sure ...