code: func builtin_shouldEscape(chr byte) bool {
  	if 'A' <= chr && chr <= 'Z' || 'a' <= chr && chr <= 'z' || '0' <= chr && chr <= '9' {
  		return false
  	}
  	return !strings.ContainsRune("*_+-./", rune(chr))
  }
docs: // escape/unescape