/usr/lib/ruby/vendor_ruby/merb-core/controller/ is in ruby-merb-core 1.1.3+dfsg-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/merb-core/controller/abstract_controller.rb
/usr/lib/ruby/vendor_ruby/merb-core/controller/exceptions.rb
/usr/lib/ruby/vendor_ruby/merb-core/controller/merb_controller.rb
/usr/lib/ruby/vendor_ruby/merb-core/controller/mime.rb
/usr/lib/ruby/vendor_ruby/merb-core/controller/mixins/
/usr/lib/ruby/vendor_ruby/merb-core/controller/mixins/authentication.rb
/usr/lib/ruby/vendor_ruby/merb-core/controller/mixins/conditional_get.rb
/usr/lib/ruby/vendor_ruby/merb-core/controller/mixins/controller.rb
/usr/lib/ruby/vendor_ruby/merb-core/controller/mixins/render.rb
/usr/lib/ruby/vendor_ruby/merb-core/controller/mixins/responder.rb
/usr/lib/ruby/vendor_ruby/merb-core/controller/template.rb