code: func (parser *Parser) parsePrelude() (string, error) {
  	result := ""
  
  	for parser.tokenParsable() && !parser.tokenEndOfPrelude() {
  		token := parser.shiftToken()
  		result += token.Value
  	}
  
  	result = strings.TrimSpace(result)
  
  	// log.Printf("[parsed] prelude: %s", result)
  
  	return result, parser.err()
  }
docs: // Parse Rule prelude