Apache and
mod_perl
at
http://www.apache.org/
.
Apache is a freely available web server that embeds a Perl interpreter. mod_perl, written by Doug MacEachern, is a Perl module that provides the glue between the Apache C API and Perl, and allows you to write to the Apache API instead of CGI scripts. People have reported 400-2000% improvement in speed over the CGI approach.