why do you check with exists anyway?

Out of habit. I consider it defensive programming. In this small example, there is no need to use exists because I have clearly set the values of all keys to 1, which is defined and true, as opposed to undef or 0.

I also kinda like how it reads.

If you can convince me there is a significant penalty (performance/memory/etc.) for using exists, then I may consider changing my habit.