Note: This is a work in progress and many formatting issues have been fixed. Read more about the project on the home page.
Handler:
HyperCard repeatedly sends the idle
message to the current card when no other events are occurring (that is, when all handlers have finished running and HyperCard itself isn’t sending other messages).
Any return-separated list of built-in commands, user-defined handlers, or keywords that are part of a message or function handler.