||Creates a temporary scripting variable based on a ViewHelper class which will not be exposed outside of the Tag scope.
||Expose a ViewHelper instance as a scripting variable if it is found
in the request scope, either under the default key or under the key
specifed by the id attribute.
||Conditionnaly include the specified file or body content
based upon the code of the
returned by the execution of the
ViewHelper instance created in the parent