Alfredo PUMEX provides a pluggable mechanism for customizing the SugarCRM Users module without modifying core files. It uses jQuery and Alfredo Patch to dynamically extend the Users module functionality. Extension modules simply provide template and PHP files that are loaded via globbing. This allows customizing detail and edit views, and intercepting save actions to handle custom fields. The document provides an example of refactoring the YAAI module to use this approach instead of overwriting core files.