Poj,

your suggestion is the right way, i will start from here.

I Just underline update is deprecated

@4000000058db6ef81e84eb6c # *** DEPRECATION WARNING ***
@4000000058db6ef81e84eb6c #
@4000000058db6ef81e84eb6c # The 'update' method will be removed in a f
+uture major release.
@4000000058db6ef81e84ef54 # Use $_, $_ or 'replace_one' instead.
[download]

so i made a little modification

    my $col = $db->get_collection('counters');
    $col->update_one({'_id' => 'comm-id'},{ '$inc' => { 'seq' => 1}});
    my $id = $col->find_one({'_id' => 'comm-id'})->{'seq'};
[download]

so now it is working.

Thanks so much, it really help!