/usr/lib/ruby/1.9.1/rdoc/markup/ is in libruby1.9.1 1.9.3.484-2ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/1.9.1/rdoc/markup/attribute_manager.rb
/usr/lib/ruby/1.9.1/rdoc/markup/blank_line.rb
/usr/lib/ruby/1.9.1/rdoc/markup/document.rb
/usr/lib/ruby/1.9.1/rdoc/markup/formatter.rb
/usr/lib/ruby/1.9.1/rdoc/markup/formatter_test_case.rb
/usr/lib/ruby/1.9.1/rdoc/markup/heading.rb
/usr/lib/ruby/1.9.1/rdoc/markup/indented_paragraph.rb
/usr/lib/ruby/1.9.1/rdoc/markup/inline.rb
/usr/lib/ruby/1.9.1/rdoc/markup/list.rb
/usr/lib/ruby/1.9.1/rdoc/markup/list_item.rb
/usr/lib/ruby/1.9.1/rdoc/markup/paragraph.rb
/usr/lib/ruby/1.9.1/rdoc/markup/parser.rb
/usr/lib/ruby/1.9.1/rdoc/markup/pre_process.rb
/usr/lib/ruby/1.9.1/rdoc/markup/raw.rb
/usr/lib/ruby/1.9.1/rdoc/markup/rule.rb
/usr/lib/ruby/1.9.1/rdoc/markup/text_formatter_test_case.rb
/usr/lib/ruby/1.9.1/rdoc/markup/to_ansi.rb
/usr/lib/ruby/1.9.1/rdoc/markup/to_bs.rb
/usr/lib/ruby/1.9.1/rdoc/markup/to_html.rb
/usr/lib/ruby/1.9.1/rdoc/markup/to_html_crossref.rb
/usr/lib/ruby/1.9.1/rdoc/markup/to_rdoc.rb
/usr/lib/ruby/1.9.1/rdoc/markup/to_test.rb
/usr/lib/ruby/1.9.1/rdoc/markup/to_tt_only.rb
/usr/lib/ruby/1.9.1/rdoc/markup/verbatim.rb