P.p.s: After thinking about why I would've been using the quantifiers outside vs inside, separate from maybe capturing only one repetition of a group, I figured it out:

Alternations. If you wanted a word among multiple choices but only 0-1 times you have a sort of choices:

(this|that|third_thing)?

((this)?|(that)?|(third_thing)?)

[download]
The first one is pretty clear, I want 0 or 1 of any of those words. It will return undef if I have 0.

The second one, I don't even trust it. I think I could match all 3 if they happen in a row. Additionally, there's probably 4 capture groups created as a result.

A quick search on if I had used 'alternation' properly: https://docstore.mik.ua/orelly/perl4/prog/ch05_08.htm
"When you apply the ? to a subpattern that captures into a numbered variable, that variable will be undefined if there's no string to go there. If you used an empty alternative, it would still be false, but would be a defined null string instead."

In reply to Re^2: Regex result being defined when it shouldn't be(?) by chenhonkhonk
in thread Regex result being defined when it shouldn't be(?) by chenhonkhonk

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