/usr/lib/ruby/ is in ruby-diff-lcs 1.3-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/diff/
/usr/lib/ruby/vendor_ruby/diff/lcs/
/usr/lib/ruby/vendor_ruby/diff/lcs/array.rb
/usr/lib/ruby/vendor_ruby/diff/lcs/block.rb
/usr/lib/ruby/vendor_ruby/diff/lcs/callbacks.rb
/usr/lib/ruby/vendor_ruby/diff/lcs/change.rb
/usr/lib/ruby/vendor_ruby/diff/lcs/htmldiff.rb
/usr/lib/ruby/vendor_ruby/diff/lcs/hunk.rb
/usr/lib/ruby/vendor_ruby/diff/lcs/internals.rb
/usr/lib/ruby/vendor_ruby/diff/lcs/ldiff.rb
/usr/lib/ruby/vendor_ruby/diff/lcs/string.rb
/usr/lib/ruby/vendor_ruby/diff/lcs.rb
/usr/lib/ruby/vendor_ruby/diff-lcs.rb