local lines = {}
for k, v in pairs(_G) do
  if type(v) == 'number' then
    table.insert(lines, k..'='..tostring(v))
  elseif type(v) == 'string' then
    table.insert(lines, k..'='..('%q'):format(v))
  end
end
return table.concat(lines, "\\n")

Initial version of #151 that could handle only numbers and strings. And no special characters in _G keys, but that is nasty anyways, nobody does it!