throw(ERROR code, STRING explanation[, ANY additional])
This function throws an error with the code code in the calling method, not the current method. The current method does not have the ability to stop an error originating in itself. The variables explanation and additional appear in the traceback. For more information on error handling see traceback() and Errors. Example:
throw(~perm, "Sender is not the system object.");
error() | rethrow() | throw() | traceback()