BerkeleyDB is a module which allows Perl programs to make use of the
facilities provided by Berkeley DB version 2 or greater.
(Note: if you want to use version 1 of Berkeley DB with Perl you
need the DB_File module).

Berkeley DB is a C library which provides a consistent interface to a
number of database formats. BerkeleyDB provides an interface to all
four of the database types (hash, btree, queue and recno) currently
supported by Berkeley DB.