Both PHP and Perl should be sufficient for your CGI scripting. According to perl.com, there is no Perl or CGI distribution for Mac servers. Macs rank in the lowest 0.01% for web servers anyway. If you'd like to check out what are the most commonly used web servers, check out http://www.netcraft.com/survey/
- Apache (running on Linux/Unix) and IIS (Microsoft) dominate the market (80% in total).
If you'd like more info on CGI scripting, check out http://www.hotscripts.com
where you can get CGI scripts (and there may be one already written, waiting for you), as well as get pointers to other useful CGI/Perl resources.