Since there is still some queries that returns empty values,

Leandro, this appears to be a bug in IO::Socket::INET::Daemon, in as much as, it frequently calls the data callback when there is nothing to available read; and getline returns undef.

I do not have the time to debug that module; but the simple workaround to it, is to move one line of code in your callback. change this:

 23        callback => { data =>
 24             sub {
 25                 my ($io, $host) = @_;
 26                 chomp( my $line = <$io> );
 27                 return 0 unless $line;      ####### MOVE THIS LINE
+ UP AND TEST FOR DEFINEDNESS ###################
 28                 $Qout->enqueue( $line );    ## send work to listen
+er (is not sending to walker ?)
 29                 return !0;
 30             }
 31         },
[download]

To become this:

 23        callback => { data =>
 24             sub {
 25                 my ($io, $host) = @_;
 26                 return 0 unless defined $line;  ################ M
+OVED LINE #####################
 27                 chomp( my $line = <$io> );
 28                 $Qout->enqueue( $line );    ## send work to walker
 29                 return !0;
 30             }
 31         },
[download]

I think that should get you further.

(And yes, the comment was wrong!).

(And BTW: you really should get into the habit of using strict and my. Debugging would have been much simpler had your code been strict compliant.)