Re^2: Possessive sub-pattern with non-greedy content + recursion: WHY does this work??

[Anonymous Monk]

simplifies to ^

Oh... I didn't understand the whole construct, then. Thanks! I guess "Possessive sub-pattern with non-greedy..., etc." can be stricken out from title. To be replaced with, start-of-string anchor and failure? Because,

Match fails -- it's irrelevant

But looks like it is. And, in parallel, comparing with look-ahead, which at 1st glance can be a simpler alternative (?):

say $-[1], ': ', $1 while 'olololo' =~ /
    (?=
        (
            (.)(?-2)\g-1 | (.).\g-1 
        )
    )
/gx;

say '*';

say 'match' if 'olololo' =~ /
    ^
    ( 
        (
            (.)(?-3)\g-1 | (.).\g-1 
        )
        (?{ 
            say $-[2], ': ', $2
        })
    )
    (?#*F)
/x;

Output:

0: olololo
1: lolol
2: ololo
3: lol
4: olo
*
4: olo
3: lol
2: ololo
2: olo
1: lolol
0: olololo
match

Look-ahead misses some PD's for obvious reasons. But match success in case of recursion leads to omission of 2 PD's, too. Why? Converting "comment" to "fail" i.e. (F*) gives all nine PD's, visited exactly once each (with some disruption to "visit in reverse" order):

4: olo
3: lol
2: ololo
2: olo
1: lolol
0: olololo
1: lol
0: ololo
0: olo

[Anonymous Monk]

omission of 2 omission of 3