Assigning to hash keys when there is a default value?

dBlack wrote:

It's really always h[k] = h.default -- it's just that the default
default, so to speak, is nil.

arggh, yes.
i guess my mind was too focused on x=x

irb(main):027:0> zz
NameError: undefined local variable or method `zz' for main:Object
        from (irb):27
irb(main):028:0> zz=zz
=> nil

kind regards -botp