Syntax
(defmessage-handler USER message-duplicate primary (?new-instance-name ?slot-override-expressions)
This handler duplicates an instance
using messages. Slot values from the original instance and slot
overrides are copied using put and get messages. If the name of
the new instance created matches a currently existing instance-name,
then the currently existing instance is deleted using a delete
message. After creation, the new instance is sent an init message.
The slot-override expressions are passed as an EXTERNAL_ADDRESS
data object to the message-duplicate handler. This message is used
by the functions message-duplicate-instance
and active-message-duplicate-instance.