# File lib/pdf/reader/explore.rb, line 86
    def ls (entry = nil)
      parts = @pwd.split('/')
      obj   = @root

      parts.shift if parts[0] == ""
      parts.push(entry) if entry

      parts.each do |p|
        case obj
        when Hash
          unless obj.has_key?(p)
            puts "invalid path at #{p}"
            return
          end
          obj = obj[p]

        when Array
          obj = obj[p.to_i]
        end

        obj = @xref.object(obj)
      end

      output_parent(obj)
      "#{@pwd}: #{obj.class}"
    end