my $hostname =
 gethostbyaddr(inet_aton($data[$ip_address_pos]), AF_INET)
         || "Can't resolve $data[$ip_address_pos]: $!\n";

my $hostname =
 (gethostbyaddr(inet_aton($data[$ip_address_pos]), AF_INET)
         or "Can't resolve $data[$ip_address_pos]: $!\n"
 );