Parsing application/x-www-form-urlencoded data
Parsing multipart/form data
Parsing HTTP cookies
The Perl modules are simply a thin XS layer on top of libapreq, making them a lighter and faster alternative to CGI.pm and CGI::Cookie. See the Apache::Request and Apache::Cookie documentation for more details and eg/perl/ for examples.
Apache::Request and libapreq are tied tightly to the Apache API, to which there is no access in a process running under mod_cgi.
Available from CPAN. See the module manpage for more information.