I'm going to print to STDERR, then have the module return a false value, assuming that mod_perl will die as gracefully as it requires if that happens. Doing that prints my error message, then a syntax error in httpd.conf message and a Foo.pm dit not return a true value message, which is fine with me.

I see in ModPerl::Util:

or use C<CORE::exit()>:

  eval {
     CORE::exit;
  }
  print "Still running";

and nothing will be printed. The problem with the latter is the
current process (or a Perl Interpreter) will be killed; something that
you really want to avoid under mod_perl.
[download]

In this case, I do want to actually kill everything, but am still concerned by that "something that you really want to avoid". I was hoping there'd be an actual mod_perl-supplied mechanism to stop the show.

What that's saying is that you don't want to exit while serving web requests. It's no problem to abort startup by calling exit.