The Perl interface to Berkeley DB version 1.85 is called DB_File. The Perl interface to Berkeley DB version 2.X is called BerkeleyDB.
DB_File is distributed with the standard Perl source distribution (look in the directory "ext/DB_File"). You can find both DB_File and BerkeleyDB on CPAN, the Comprehensive Perl Archive Network of mirrored FTP sites. The master CPAN site is ftp://ftp.funet.fi/.
Questions about DB_File and BerkeleyDB are best asked on the Usenet newsgroup comp.lang.perl.modules.