Remove element / function Corona SDK

I have form.lua file with code:

local _M = {}

function _M.calc( a )

    local quad = display.newRect(100,100,100,100)
end
return _M

and the file scene2.lua with the code:

local form = require "form"

form.calc( )

I need the quad / function to be removed from the screen when I go to another scene.