It appears as though $test->{dest} is a hash of NetPacket::TCP objects keyed on some id that, as you've noticed, varies, so, given that $test->{dest}->{num} is a hash ref., in order to see the flags for all dest's, try...

foreach my $num (keys %{ $test->{dest} } ) {
    print "$num: " . $test->{dest}->{$num}->flags();
}
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