OK, I've made significant progress with a lot of reading.
I have learned more than I wanted to know about the whole setuid issue, and have written a C++ wrapper to call the script and pass the command-line issues. I then gave the C++ program more appropriate access permissions.
I then went through and did all the necessary sanity-checking and untainting of the various data.
I then got to my favorite part of any coding process, debugging!
After several failed attempts, I got

"su -c './perl_run Build' nobody"
[download]

to work correctly.
Thinking I was all but done, I included the system call to the script my $results = system("/usr/local/bin/perl/perl_run", $directive); in my CGI program. Before untainting, I would get -1 for results, which I expected, as it didn't work at that time.

However, now I'm getting 256 (which I believe is actually '1' for success) but here's the catch:
The program isn't running, the site isn't changing, and I'm about to call it quits in favor of a few tall mugs of Newcastle.

Any thoughts?
cidaris