OK and update... this worked:

for my $key (keys %{$conn->tcp_connection->window->{dest}}){
my $cb = ${$conn->tcp_connection->window->{dest}}{$key};
print  $cb->{src_port} . "\n\n\n";
}
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The reason is that it as far as i can tell, loops through .. and enumerates the name of the value after dest. This is the first in the loop above. But is the a way i can say .... use first instance ... insted of looping through it ???