The head vs. HEAD problem is a well-known problem with using CPAN on Mac OS X. There was some discussion on this list last month because some people believed that the problem had been fixed. Sadly, your experience proves otherwise.
I actually also had it interfere with configuring mod_perl on Mac OS X. So it's _not_ limited to just using CPAN. Removing /usr/local/bin/head from the system (exposing the original /usr/bin/head again) solved that problem for me.
Liz
