/usr/lib/ruby/2.0.0/tkextlib/blt/ is in ruby2.0-tcltk 2.0.0.484-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/2.0.0/tkextlib/blt/barchart.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/bitmap.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/busy.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/component.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/container.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/cutbuffer.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/dragdrop.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/eps.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/graph.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/htext.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/setup.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/spline.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/stripchart.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/table.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/tabnotebook.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/tabset.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/ted.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/tile/
/usr/lib/ruby/2.0.0/tkextlib/blt/tile.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/tile/button.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/tile/checkbutton.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/tile/frame.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/tile/label.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/tile/radiobutton.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/tile/scrollbar.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/tile/toplevel.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/tree.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/treeview.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/unix_dnd.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/vector.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/watch.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/win_printer.rb
/usr/lib/ruby/2.0.0/tkextlib/blt/winop.rb