Well, I do seam to have a misconfigured perl.
I've just entered:
/usr/local/cpanel/whostmgr/docroot/cgi/diskusage.cgi as a test, and I get the same type of errors.
Although a basic hello-world.cgi in a domain does work. that obviously doesn't require any libs.
So I guess I need to reinstall perl. Now it's off to find out how I do that.
first I'll go to whm/software/update system software, ... everything fine down to:
make[2]: Leaving directory `/home/cpgdbuild/gd-2.0.33'
make[1]: Leaving directory `/home/cpgdbuild/gd-2.0.33'
GD install failed and I'm stuck here. So, I'll search around and see if I can find a solution. I believe the main problem was a manual perl update to 5.8.6 which I problably should not have done. ( especially as I am a gumby )