Try looking at your system's Berkely DB installation... you may have either a broken one or multiple installed berkeley versions confusing things. db.h usually is in /usr/include (or a subdirectory corresponding to what Linux thinks its base version should be, like /usr/include/db4), not to mention that the line -I/usr/local/BerkeleyDB/include is pointing it to a Berkeley db install in /usr/local/ (doesn't sound standard redhat to me)

Try installing an rpm of DB_File instead of CPAN source.. might save lots of time..