Ideas? Gosh, where does one learn this stuff?

What is there to learn (the message say it all)?

"/System/Library/Perl/5.8.1/darwin-thread-multi-2level/CORE/perl.h" does not exist, which means your perl install is broken.

All these 3rd party binary installations are really annoying, mostly because people don't know what to do when things break.

Install perl by compiling it from sources yourself. The various INSTALL files cover everything you need to know.