Mandrake 10 Perl 5.8.3 CORE didn't come with config.h and other files that were asked for by Make...
I downloaded ActiveState Perl 5.8.4, which I've been very happy with before on Win32, and sure enough it comes with loads of files already setup in CORE.
CPAN installation of Tk and Tk-Pod then succeeded with no problems, so I'm converting over to the Active State Perl.
I still don't know what the CORE files are used for, can anybody tell me ?