code: func isTerminator(r rune) bool {
  	if isSpace(r) || isEndOfLine(r) {
  		return true
  	}
  	switch r {
  	case eof, '.', ',', '[', ']', '$', '@', '{', '}':
  		return true
  	}
  	return false
  }
docs: // isTerminator reports whether the input is at valid termination character to appear after an identifier.