BerkeleyDB is a module that 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 that 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.