static S unquote_accurate(S s) {

  if (s == null) null;

  if (startsWith(s, '[')) {

    int i = 1;

    while (i < s.length() && s.charAt(i) == '=') ++i;

    if (i < s.length() && s.charAt(i) == '[') {

      String m = s.substring(1, i);

      if (s.endsWith("]" + m + "]"))

        return s.substring(i+1, s.length()-i-1);

    }

  }

  int l = s.length();

  if (l > 1) {

    char opener = s.charAt(0);

    if (opener == '\"' || opener == '\'') {

      if (s.charAt(l-1) != opener) ret s;

      --l;

      StringBuilder sb = new StringBuilder(l);

      for (int i = 1; i < l; i++) {

        char ch = s.charAt(i);

        if (ch == opener) ret s; // improper string

        if (ch == '\\') {

          char nextChar = (i == l - 1) ? '\\' : s.charAt(i + 1);

          // Octal escape?

          if (nextChar >= '0' && nextChar <= '7') {

              String code = "" + nextChar;

              i++;

              if ((i < l - 1) && s.charAt(i + 1) >= '0'

                      && s.charAt(i + 1) <= '7') {

                  code += s.charAt(i + 1);

                  i++;

                  if ((i < l - 1) && s.charAt(i + 1) >= '0'

                          && s.charAt(i + 1) <= '7') {

                      code += s.charAt(i + 1);

                      i++;

                  }

              }

              sb.append((char) Integer.parseInt(code, 8));

              continue;

          }

          switch (nextChar) {

          case '\"': ch = '\"'; break;

          case '\\': ch = '\\'; break;

          case 'b': ch = '\b'; break;

          case 'f': ch = '\f'; break;

          case 'n': ch = '\n'; break;

          case 'r': ch = '\r'; break;

          case 't': ch = '\t'; break;

          case '\'': ch = '\''; break;

          // Hex Unicode: u????

          case 'u':

              if (i >= l - 5) {

                  ch = 'u';

                  break;

              }

              int code = Integer.parseInt(

                      "" + s.charAt(i + 2) + s.charAt(i + 3)

                         + s.charAt(i + 4) + s.charAt(i + 5), 16);

              sb.append(Character.toChars(code));

              i += 5;

              continue;

          default:

            ch = nextChar; // added by Stefan

          }

          i++;

        }

        sb.append(ch);

      }

      ret sb.toString();

    }

  }

  ret s; // not quoted - return original

}