my $checkPort = sub {
    my $port = shift;
    if ($port) {
        if ($port > MAX_PORT or $port < MIN_PORT){
        $error = "Please insert a correct port number (".MIN_PORT." - 
+".MAX_PORT.")";
        return TRUE;
        }
    }
    else {
        $moduleInput{-port} = 123;
        return FALSE;
    }
    };