Authen::PluggableCaptcha is a fully modularized and extensible system for
making Pluggable Catpcha (Completely Automated Public Turing Test to Tell
Computers and Humans Apart) tests.

Pluggable? All Captcha objects are instantiated and interfaced via the main
module, and then manipulated to require various submodules as plug-ins.

Authen::PluggableCaptcha borrows from the functionality in
Apache::Session::Flex

WWW: https://metacpan.org/release/Authen-PluggableCaptcha