[erlang-questions] How do things like module dict impleented to work fast?

[Dmitry Kakurin]

Newbie question.
When I append something to a dictionary a new copy is returned and the
old copy is still valid (the functional nature of Erlang).
I've assumed that there is some kind of clever trick to create an
appearance of copy without actual data duplication.
However after looking at dict sources it looks like it does a simple copy.
Am I missing something or there is no trick?

- Dmitry