Byte.com: Learning Perl, Part III – Applying Perl To Websites

“Common Gateway Interface (CGI) programs are a standard,
portable way to write Web-based applications. CGI programs can
be written in almost any programming or scripting language that you
care to run on your server, but Perl is far and away the most
common language used for writing CGI scripts.

“CGI is useful in several scenarios. The most common scenario is
form processing: the website displays an HTML form to the user, and
the user fills out the form. When the user submits the form, its
contents are sent to a CGI script on the site for processing.
Typically, the output of the form processing is a customized Web
page, one or more e-mail, and/or a database entry….”

“Combining a database with dynamic page generation turns out to
be extremely powerful. This is how most of the Internet search
engines work, for instance, and how most shopping sites work.”