exception messages

[Greg]

I'm attempting to learn D through a personal project, and can't 
figure out how to get the message from an exception.  I've 
basically defined a custom subclass of Exception to represent 
when invalid inputs are provided, and would like to have a master 
catch block that handles them, but I can't find API docs for 
Throwable or Exception within the Phobos Library Reference.   In 
particular, I can't find API definitions for those classes in 
either std.exception or core.exception.  Where else should I be 
looking?