copy.lua

local function copy(inp,copies)
  local todo = {[inp] = {}}
  copies = type(copies) == "table" and copies or {}
  copies[inp] = todo[inp]
  -- we can't use pairs or for here because we modify todo
  while next(todo) do
    local i,o = next(todo)
    todo[i] = nil
    for k,v in next,i do
      if copies[k] ~= nil then
        k = copies[k]
      elseif type(k) == "table" then
        local t = {}
        todo[k] = t
        copies[k] = t
        k = t
      end
      if copies[v] ~= nil then
        v = copies[v]
      elseif type(v) == "table" then
        local t = {}
        todo[v] = t
        copies[v] = t
        v = t
      end
      rawset(o,k,v)
    end
  end
  return copies[inp] -- heh :P
end