--[[ CURRENT ]]
local key_handlers = {
        -- execution and actions
        ["Mod1-Return"] = function (key)
                local xterm = get_conf("xterm") or "xterm"
                execute (xterm .. " &")
        end,
}

--[[ PROPOSED ]]
grabmod = get_ctl("grabmod")
local key_handlers = {
        -- execution and actions
        [grabmod .. "-Return"] = function (key)
                local xterm = get_conf("xterm") or "xterm"
                execute (xterm .. " &")
        end,
}