The FIND method determines
whether the key exists in the hash object. The HAS_PREV method determines
whether the key has multiple data items associated with it. When you
have determined that the key has a previous data item, that data item
can be retrieved by using the FIND_PREV method, which sets the data
variable to the value of the data item so that it is available for
use after the method call. Once you are in the data item list, you
can use the HAS_PREV and FIND_PREV methods in addition to the HAS_NEXT
and FIND_NEXT methods to traverse the list.
See HAS_NEXT Method for an example.