The major problem with CGI is that it launches your script for every request. For large frameworks such as Catalyst, which can use dozens of modules, the startup time can be huge, making CGI impractical.

Popular replacements for CGI are mod_perl, which embeds libperl as an Apache module, and FastCGI, which runs your script as a separate long-lived process. Although they interact with the server in very different ways, they both accomplish one key goal - they avoid the heavy startup costs by compiling your code once, then executing it many times.