That's for sure possible in a sole RegEx without while loop just with a /g-modifier!
No. A regexp cannot print anything. Somewhere, you need to execute code, either outside a regexy construct, in the replacement part of an s/// with the /e modifier, or by using (?{ }) or (??{ }).

But if I'm allowed to execute code, than the constraint "do it in a single regexp" isn't a constraint at all. Then I just do /^(?{ code to generate whatever you want })/.

I suggest to be more specific in what you (dis)allow to have a more fun challenge.

In reply to Re: Resetting pos() within a RegEx? by JavaFan
in thread Resetting pos() within a RegEx? by LanX

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