Ugh. I seem to be good at answering my own ?'s. The problem is not with the code, the problem is with mod_perl. In particular, I simply needed to restart Apache. (sheepish grin)

Anyone who is having weird errors and warnings writing CGI scripts under mod_perl should go here:

http://www.perlreference.com/mod_perl/guide/warnings.html

There are quite a few quirks out there...