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Retrieves the hostname (and alternate addresses) of a packed binary network address . ( addrtype indicates the type of address given. Since gethostbyaddr is used almost solely for Internet IP addresses, addrtype is not needed.) The return value in list context is:

($name, $aliases, $addrtype, $length, @addrs)
where @addrs is a list of packed binary addresses. In the Internet domain, each address is four bytes long and can be unpacked by saying something like:
($a, $b, $c, $d) = unpack('C4', $addrs[0]);
In scalar context, gethostbyaddr returns only the hostname.