local function merge_maps(m1, m2)
    local m3 = {}
    for m1:keys() as key do m3[key] = m1[key] end
    for m2:keys() as key do m3[key] = m2[key] end
    return m3
end

local base = {name = "Rocket Skates", price = 12.75, color = "yellow"}
local update = {price = 15.25, color = "red", year = 1974}
local merged = merge_maps(base, update)
for k, v in merged do print(k, v) end