@Override
    public char getIndicator() {
        final int len = source.length();
        char ind = (len > 0) ? source.charAt(0) : ' ';
        switch (ind) {
            case '*':
            case '/':
            case '$': break;
            case 'D': //    Debugging line is marked by a 'D'/'d' followed
            case 'd': //    by space.
                char next = (len > 1) ? source.charAt(1) : ' ';
                ind = (next == ' ') ? ind : ' ';
                break;
            default : ind = ' ';
        }
        return ind;
    }