# File lib/mail/parsers/rfc2045.rb, line 286
    def _nt_custom_x_token
      start_index = index
      if node_cache[:custom_x_token].has_key?(index)
        cached = node_cache[:custom_x_token][index]
        if cached
          cached = SyntaxNode.new(input, index...(index + 1)) if cached == true
          @index = cached.interval.end
        end
        return cached
      end

      i0, s0 = index, []
      if has_terminal?('\G[xX]', true, index)
        r1 = true
        @index += 1
      else
        r1 = nil
      end
      s0 << r1
      if r1
        if has_terminal?("-", false, index)
          r2 = instantiate_node(SyntaxNode,input, index...(index + 1))
          @index += 1
        else
          terminal_parse_failure("-")
          r2 = nil
        end
        s0 << r2
        if r2
          s3, i3 = [], index
          loop do
            r4 = _nt_token
            if r4
              s3 << r4
            else
              break
            end
          end
          if s3.empty?
            @index = i3
            r3 = nil
          else
            r3 = instantiate_node(SyntaxNode,input, i3...index, s3)
          end
          s0 << r3
        end
      end
      if s0.last
        r0 = instantiate_node(SyntaxNode,input, i0...index, s0)
        r0.extend(CustomXToken0)
      else
        @index = i0
        r0 = nil
      end

      node_cache[:custom_x_token][start_index] = r0

      r0
    end