/usr/lib/ruby/ is in magicmaze 1.4.3.6+dfsg-3~deb9u1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/magicmaze/
/usr/lib/ruby/vendor_ruby/magicmaze/entity.rb
/usr/lib/ruby/vendor_ruby/magicmaze/filemap.rb
/usr/lib/ruby/vendor_ruby/magicmaze/game.rb
/usr/lib/ruby/vendor_ruby/magicmaze/gameloop.rb
/usr/lib/ruby/vendor_ruby/magicmaze/graphics.rb
/usr/lib/ruby/vendor_ruby/magicmaze/images.rb
/usr/lib/ruby/vendor_ruby/magicmaze/input.rb
/usr/lib/ruby/vendor_ruby/magicmaze/inventory.rb
/usr/lib/ruby/vendor_ruby/magicmaze/magicmaze.rb
/usr/lib/ruby/vendor_ruby/magicmaze/map.rb
/usr/lib/ruby/vendor_ruby/magicmaze/mapeditor.rb
/usr/lib/ruby/vendor_ruby/magicmaze/movement.rb
/usr/lib/ruby/vendor_ruby/magicmaze/player.rb
/usr/lib/ruby/vendor_ruby/magicmaze/sound.rb
/usr/lib/ruby/vendor_ruby/magicmaze/spellbook.rb
/usr/lib/ruby/vendor_ruby/magicmaze/spelltile.rb
/usr/lib/ruby/vendor_ruby/magicmaze/test_filemap.rb
/usr/lib/ruby/vendor_ruby/magicmaze/test_game.rb
/usr/lib/ruby/vendor_ruby/magicmaze/test_graphics.rb
/usr/lib/ruby/vendor_ruby/magicmaze/test_images.rb
/usr/lib/ruby/vendor_ruby/magicmaze/test_magicmaze.rb
/usr/lib/ruby/vendor_ruby/magicmaze/test_map.rb
/usr/lib/ruby/vendor_ruby/magicmaze/test_movement.rb
/usr/lib/ruby/vendor_ruby/magicmaze/test_player.rb
/usr/lib/ruby/vendor_ruby/magicmaze/test_sound.rb
/usr/lib/ruby/vendor_ruby/magicmaze/test_tile.rb
/usr/lib/ruby/vendor_ruby/magicmaze/tile.rb