Take two seconds to think what you want to check. All the nics have a device, so that's obviously not it.

for my $nic (networkInfo()) {
    if (defined($nic->{ip}) {
        print "DeviceMain: $nic->{device} " .
            "has IP Address $nic->{ip}\n" .
            "\tMask: $nic->{mask}\n" .
            "\tBroadcast: $nic->{bcast}\n";
    }     

    if (defined($nic->{ip6}) {
        print "DeviceMain: $nic->{device} " .
            "has IPv6 address $nic->{ip6}\n";
    }
}
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(Made the lines shorter to avoid PM's wrapping.)