In addition to the key-value pairs accepted by IO::Socket,  "IO::Socket::INET6" provides.

               Domain      Address family               AF_INET | AF_INET6 | AF_UNSPEC (default)


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           If "Domain" is not given, AF_UNSPEC is assumed, that is, both AF_INET and AF_INET6 will be both considered when resolving DNS  names. AF_INET6 is prioritary. 


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           (Concrete to IPv4 protocol)

              $sock = IO::Socket::INET6->new(PeerAddr => 'www.perl.org',
                                            PeerPort => 'http(80)',
                                            Domain => AF_INET ,
                                            Proto    => 'tcp');