CGI::Fast is a subclass of the CGI object created by CGI.pm. It is
specialized to work with the FCGI module, 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.

Note that as CGI::Fast is based on CGI.pm it is no longer advised as a
way to write Perl web apps.