Params::callbackrequest provides functional and object-oriented callbacks to method and function parameters. callbacks may be either code references provided to the new() constructor, or methods defined in subclasses of params::callback. callbacks are triggered either for every call to the params::callbackrequest request() method, or by specially named keys in the parameters to request().

the idea behind this module is to provide a sort of plugin architecture for perl templating systems. callbacks are triggered by the contents of a request to the perl templating server, before the templating system itself executes. this approach allows you to carry out logical processing of data submitted from a form, to affect the contents of the request parameters before they're passed to the templating system for processing, and even to redirect or abort the request before the templating system handles it.