CGI::Fast comes with the standard CGI module. You can get CGI::Fast from any CPAN site. To quote from the CGI::Fast documentation:

CGI::Fast is a subclass of the CGI object created by CGI.pm. It is specialized to work well with the Open Market FastCGI standard, which greatly speeds up CGI scripts by turning them into persistently running server processes. Scripts that perform time-consuming initialization processes, such as loading large modules or opening persistent database connections, will see large performance improvements.

If you really want to speed-up your website there are other tools that you should also explore (mod_perl to start with).