This tests for a valid Exception object:

The following expression is not a valid Exception object:

This tests that the passed expression is a valid Exception object of type tag, or its subtypes:

This registers the exception type as a child of some other exception type:

This confirms that the passed expression is a valid Exception object of type "GeneralError":

This deregisters the exception type:

This tests an unrelated Exception object, and the types do not match:

For a list of types in the second argument of ExceptionQ, a single match is sufficient to give True:

This returns False, because ExceptionQ is applied to an unevaluated Exception constructor call:

When applied to the fully evaluated Exception constructor, ExceptionQ produces True, as expected:

This registers the exception type logicalError as a child of type "GeneralError":

This defines the custom exception handler that rethrows exceptions of the type "GeneralError", and converts all other exceptions to Failure objects:

In this case, some generic exception is converted to a Failure:

In this case, exception of the type logicalError is rethrown, because logicalError is a subtype of "GeneralError":