Clone vs Copy - any libs for that?

[zgrssd]

I ran into the small issues that tables are generally handed to and from function by reference instead of by value. So I need to channel my inner mad scientist and start cloning.

Some search gave me these code for shallow and deep cloning respectively:

function copy (t) -- shallow-copy a table
    if type(t) ~= "table" then return t end
    local meta = getmetatable(t)
    local target = {}
    for k, v in pairs(t) do target[k] = v end
    setmetatable(target, meta)
    return target
end

function clone (t) -- deep-copy a table
    if type(t) ~= "table" then return t end
    local meta = getmetatable(t)
    local target = {}
    for k, v in pairs(t) do
        if type(v) == "table" then
            target[k] = clone(v)
        else
            target[k] = v
        end
    end
    setmetatable(target, meta)
    return target
end

Now I don't understand enough about metatables, tables and lua in general to be certain if that is code right (it looks like it).
And of course it could help to fold both functions into one with a bool switch/int to tell the maximum depth to clone.

Has annybody already written some code for cloning in his library so I don't repeat the same code?