I do not know of any mod_perl for iplanet. Where I work, QWest (formaly US West), we use iplanet and perl a lot. I haven't noticed any problems with performance, even on older servers. If you want to improve performance you can always write a deamon that can handle multiple requests, but I don't think that is necessary. The best advice I can give you is to test it out, perform benchmarks to see how your server can handle the stress.