/usr/lib/ruby/vendor_ruby/ is in ruby-mathml 0.14-4.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/math_ml.rb
/usr/lib/ruby/vendor_ruby/math_ml/
/usr/lib/ruby/vendor_ruby/math_ml/latex.rb
/usr/lib/ruby/vendor_ruby/math_ml/symbol/
/usr/lib/ruby/vendor_ruby/math_ml/symbol/entity_reference.rb
/usr/lib/ruby/vendor_ruby/math_ml/symbol/character_reference.rb
/usr/lib/ruby/vendor_ruby/math_ml/symbol/utf8.rb
/usr/lib/ruby/vendor_ruby/math_ml/util.rb
/usr/lib/ruby/vendor_ruby/math_ml/string.rb
/usr/lib/ruby/vendor_ruby/math_ml/latex/
/usr/lib/ruby/vendor_ruby/math_ml/latex/builtin/
/usr/lib/ruby/vendor_ruby/math_ml/latex/builtin/symbol.rb
/usr/lib/ruby/vendor_ruby/math_ml/latex/builtin.rb
/usr/lib/ruby/vendor_ruby/math_ml/element.rb