Including flags as a bonus option in rotational-cipher

I would like to know what you think about this proposal for rotational cipher: in Bonus part B you need to create non-standard string literals like:

> R12"abc"
> R23"abc"

and so on but this problem is a good opportunity to work with flags. Because while you can research a lot to find how to define macros inside a loop, which is not easy (the problem is marked as easy), it’s not difficult to work with flags. Something like that:

macro R_str(p,flag)
    rotate(flag, p)

and we could test like:

julia> R"hello"3

julia> R"abc"1

julia> R"abc"244

We could test random numbers with:

for n in rand(1:26, 10)
    @eval @test @R_str("abc", $n)

That doesn’t necessarily apply to the bonus tasks as they’re fully optional and you can revisit them later on.