my $done = AnyEvent->condvar;
my $nt_filter = AnyEvent::Twitter::Stream->new(
           username => 'username',
           password => 'pass',
           method => 'filter',
           follow => join(',', @uids),
            on_tweet => sub {
                  my $tweet = shift;
                  my $file = "path/to/file";
                  open(FILE, ">", $file);
                  close(FILE);

                  my $json_output = to_json($tweet, {utf8 => 1});
                  # some function calls
            },
            on_error => sub {
                my $error = shift;
                debug "ERROR: $error";
            },
            timeout => 45,
        );
       $done->recv;