My suggestion would be to stay away from mod_perl 1.99.x at all costs. It's no longer maintained. There are bugs, not to mention the API changes. You'll run into issues trying to use other mod_perl related CPAN modules that only work with 2.0.x. Also, if you run into any problems and ask for help 99% of the time everyone is going to tell you to upgrade to 2.0.x to see if that fixes your problem.