title: how to use the debug library to interact with a required lua file's upvalues
body: <p>If I have a Lua function <code>f</code> I can look at all the upvalues in <code>f</code>'s closure by using the <code>debug.getupvalue</code> function. Similarly if I have a file <code>foo.lua</code> I can look at the upvalues by first doing <code>foo = loadfile(foo)</code> then using <code>debug.getupvalue</code> in the same way that you would for <code>f</code>. If I <code>require</code> <code>foo.lua</code> is there anyway I can figure out what the upvalues for the closure of <code>foo.lua</code> are?</p>