[erlang-questions] message copying or by reference

[Damien Morton]

When I send a message from one process to another on the same node, is 
that message passed by copying or by reference.

Lets say I have an agent which is maintaining a largish internal state 
(i.e. several 10s ro 100s of KB when serialised) and wants to send a 
good portion of that to another process (i.e. if the state is thought of 
as a tree, then several subtrees might be sent). How is this handled?