/usr/lib/ is in libfssm-ruby1.8 0.1.4-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/
/usr/lib/ruby/1.8/
/usr/lib/ruby/1.8/fssm.rb
/usr/lib/ruby/1.8/fssm/
/usr/lib/ruby/1.8/fssm/monitor.rb
/usr/lib/ruby/1.8/fssm/path.rb
/usr/lib/ruby/1.8/fssm/pathname.rb
/usr/lib/ruby/1.8/fssm/support.rb
/usr/lib/ruby/1.8/fssm/tree.rb
/usr/lib/ruby/1.8/fssm/backends/
/usr/lib/ruby/1.8/fssm/backends/fsevents.rb
/usr/lib/ruby/1.8/fssm/backends/inotify.rb
/usr/lib/ruby/1.8/fssm/backends/polling.rb
/usr/lib/ruby/1.8/fssm/backends/rubycocoa/
/usr/lib/ruby/1.8/fssm/backends/rubycocoa/fsevents.rb
/usr/lib/ruby/1.8/fssm/state/
/usr/lib/ruby/1.8/fssm/state/directory.rb
/usr/lib/ruby/1.8/fssm/state/file.rb