# File lib/kwartz/parser.rb, line 518
    def _parse_tuples
      line = scan_line()
      items = line.split(/,\s+/)
      tuples = []
      items.each do |item|
        unless item =~ /(.*?)=>(.*)/
          raise parse_error("'#{item}': invalid pattern.")
        end
        key = $1;   key.strip!
        val = $2;   val.strip!
        if key =~ /\A"(.*)"\z/
          key = $1
        elsif key =~ /\A'(.*)'\z/
          key = $1
        else
          raise parse_error("'#{key}': key must be \"...\" or '...'.")   #
        end
        tuples << [key, val]
      end
      return tuples
    end