Use resolv.pl instead of dig  (This fixes a whole host of problems,
not the least of which is speed, but puts more trust in Perl's resolver)

Compare serial numbers of all NS servers and report differences.
(a la doc)

Check for illegal all-numeric components.  (excepting PTR, where
the reverse check is made)

Check SOA contact and master fields for illegal addresses

Check RP records that they point to a TXT record.
