This event allows you to catch any action mode passed to the DokuWiki dispatcher act_dispatch() in inc/actions.php before it begins to process the $ACT variable itself.
The AFTER action is never performed on a successful save.
$data is a scalar containing the $ACT value (the do variable in the query string - uncleaned).
The following plugins are known to handle this event and their source code may be a good start for understanding and implementing a handler yourself.