scope

function scope(body)
    local list,res={}
    local function auto(close,msg)
        return function(t)
            if type(t)~='table' then error("need table: { expression }",2) end
            if t[1] then table.insert(list,{ arg=t[1], fn=close or io.close })
            else
                if msg=='weak' then return table.unpack(t) end
                error(msg or t[2] or "no resource",2)
            end
            return table.unpack(t)
        end
    end
    local function defer(fn) auto(fn){true} end
    local ok,err=pcall(function() res={body(auto,defer)} end)
    for i=#list,1,-1 do list[i].fn(list[i].arg) end
    if not ok then
        if type(err)~='string' then error(err,2)
        else error("scope error\nlua: "..err,2) end
    end
    return table.unpack(res)
end