Simple relative require in Lua

foo.bar.lua

require 'baz'

foo.baz.lua

print "I'm in baz!"

test.lua

local oldrequire = require

function require(modname)
  local regular_loader = package.loaders[2]
  local loader = function(inner)
    if string.match(modname, '(.*)%.') then
      return regular_loader(string.match(modname, '(.*)%.') .. '.' .. inner)
    end
  end

  table.insert(package.loaders, 1, loader)
  local retval = oldrequire(modname)
  table.remove(package.loaders, 1)

  return retval
end

require 'foo.bar'