Why are you so interested in this?
Nobody really cares as long as there is no repetition.
:)
Anyway think of this old counting machines with numbers on wheels, if one of the wheels changed from 9 to 0 it also incremented the one the the left, and so on. So 19++ becomes 20.
That's totally the same thing, only difference is that we have three different kind of wheels.
They are either
- digits 0-9
- lowercase a-z
- uppercase A-Z
> if I do my $foo = "Bz"; print ++$foo; it prints "Ca".
"z" is at the upper limit like 9, when changing to the start "a" it has to increment the next position, but within it's symbol group. "C" follows "B" like 2 followed 1 when incrementing 19.
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