The following example is from the garbage collector and uses wordlists to separate public words from helper words:
get-current ( wid )
vocabulary garbage-collector also garbage-collector definitions
... \ define helper words
( wid ) set-current \ restore original (i.e., public) compilation wordlist
... \ define the public (i.e., API) words
\ they can refer to the helper words
previous \ restore original search order (helper words become invisible)