These are simple tests for Lua.  Some of them contain useful code.
They are meant to be run to make sure Lua is ok and also to be read, to see
how Lua programs can look like.
In the directory examples/, there is more useful code, such as a library for
complex arithmetic (a good example of fallbacks for overloading and redefinition
of primitive functions), and a library for PostScript output.  Both libraries
include simple examples.