"(code) Resolve list of DNS names" thread might be worth a looksee, Baz.   Is how I automate bulk forward lookups, and includes links to a few CPAN modules of possible interest for reverse-lookupping.
    cheers,
    Don
    striving toward Perl Adept
    (it's pronounced "why-bick")

In reply to Re: Reverse DNS lookup on a list of ip addresses (relevant thread) by ybiC
in thread Reverse DNS lookup on a list of ip addresses by Baz

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