_=setmetatable({},{
    __call=function()end,
    __pow=function(s,_)
        getfenv()[_[1]]=type(_[2])=="function"and(setmetatable({_[2]},{__index=function(___,__)___[1](unpack(__))end}))or(_[2])
    end
})

_(_^{"sum",function(...)_(_^{"x",0})for i=1,#({...})do x=x+({...})[i]end print(x)end})
_(sum[{5,10,15}])