'CGI::Application::Plugin::CAPTCHA' allows programmers to easily add and
verify CAPTCHAs in their CGI::Application-derived web applications.

A CAPTCHA (or Completely Automated Public Turing Test to Tell Computers and
Humans Apart) is an image with a random string of characters. A user must
successfully enter the random string in order to submit a form. This is a
simple (yet annoying) procedure for humans to complete, but one that is
significantly more difficult for a form-stuffing script to complete without
having to integrate some sort of OCR.

CAPTCHAs are not a perfect solution. Any skilled, diligent cracker will
eventually be able to bypass a CAPTCHA, but it should be able to shut down
your average script-kiddie.