/usr/share/lua/5.2/pl/Set.lua is in lua-penlight 1.2.1-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/lua/5.2/pl/../../5.1/pl/Set.lua
/usr/share/lua/5.2/pl/../../5.1/pl/Set.lua