/usr/lib/ruby/ is in ruby-naught 1.0.0-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/naught.rb
/usr/lib/ruby/vendor_ruby/naught/
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/command.rb
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/commands.rb
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/commands/
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/commands/predicates_return.rb
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/commands/mimic.rb
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/commands/define_explicit_conversions.rb
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/commands/define_implicit_conversions.rb
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/commands/singleton.rb
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/commands/impersonate.rb
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/commands/pebble.rb
/usr/lib/ruby/vendor_ruby/naught/null_class_builder/commands/traceable.rb
/usr/lib/ruby/vendor_ruby/naught/basic_object.rb
/usr/lib/ruby/vendor_ruby/naught/conversions.rb
/usr/lib/ruby/vendor_ruby/naught/version.rb
/usr/lib/ruby/vendor_ruby/naught/null_class_builder.rb