My speculation for the first one is: As the entire regex is optional (*), it matches the (implied) null string at the begining of the bound string, so the match is true and the outer capture is that null string, hence $1=''. However, the inner capture cannot be satisfied from the outer capture, so it is undef.
For the second: Whilst the outer capture group is optional, it contains non-optional inner groupings, therefore an attempt must be made to satisfy those inner grouping before the truth of the match can be determined. As the outer capture is an or condition, and the first character in the string matches the left-most element of that or, the match is made and no further attempt is needed. At this point, the left-most inner capture group has matched 'a' so $2='a', no attempt has been made to match the right-most inner capture group, so $3=undef. The outer capture group is whatever matched inside it, so $1='a' as well.
And I would never have guessed anywhere close until I ran the code.
Okay you lot, get your wings on the left, halos on the right. It's one size fits all, and "No!", you can't have a different color.
Pick up your cloud down the end and "Yes" if you get allocated a grey one they are a bit damp under foot, but someone has to get them.
Get used to the wings fast cos its an 8 hour day...unless the Govenor calls for a cyclone or hurricane, in which case 16 hour shifts are mandatory.
Just be grateful that you arrived just as the tornado season finished. Them buggers are real work.
In reply to Re: Interesting Regex Behavior
by BrowserUk
in thread Interesting Regex Behavior
by japhy
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