Interesting. I just noticed
(|f+) behaves the same.
Running a simplified code with use re 'debug' gives the answer:
use re 'debug';
$s = 'xfx';
while ($s =~ / (f*?) /gx) {
Compiling REx " (f*?) "
Final program:
1: OPEN1 (3)
3: MINMOD (4)
4: STAR (7)
5: EXACT <f> (0)
7: CLOSE1 (9)
9: END (0)
minlen 0
xfx
------------
Matching REx " (f*?) " against "xfx"
0 <> <xfx> | 1:OPEN1(3)
0 <> <xfx> | 3:MINMOD(4)
0 <> <xfx> | 4:STAR(7)
0 <> <xfx> | 7: CLOSE1(9)
0 <> <xfx> | 9: END(0)
Match successful!
matched (f*?) of "", starting at offset of 0, ending at pos of 0
Matching REx " (f*?) " against "xfx"
0 <> <xfx> | 1:OPEN1(3)
0 <> <xfx> | 3:MINMOD(4)
0 <> <xfx> | 4:STAR(7)
0 <> <xfx> | 7: CLOSE1(9)
0 <> <xfx> | 9: END(0)
Match possible, but length=0 is smaller than requested=1, failing!
EXACT <f> can match 0 times out of 1
+...
failed...
1 <x> <fx> | 1:OPEN1(3)
1 <x> <fx> | 3:MINMOD(4)
1 <x> <fx> | 4:STAR(7)
1 <x> <fx> | 7: CLOSE1(9)
1 <x> <fx> | 9: END(0)
Match successful!
matched (f*?) of "", starting at offset of 1, ending at pos of 1
Matching REx " (f*?) " against "fx"
1 <x> <fx> | 1:OPEN1(3)
1 <x> <fx> | 3:MINMOD(4)
1 <x> <fx> | 4:STAR(7)
1 <x> <fx> | 7: CLOSE1(9)
1 <x> <fx> | 9: END(0)
Match possible, but length=0 is smaller than requested=1, failing!
EXACT <f> can match 1 times out of 1
+...
2 <xf> <x> | 7: CLOSE1(9)
2 <xf> <x> | 9: END(0)
Match successful!
matched (f*?) of "f", starting at offset of 1, ending at pos of 2
Matching REx " (f*?) " against "x"
2 <xf> <x> | 1:OPEN1(3)
2 <xf> <x> | 3:MINMOD(4)
2 <xf> <x> | 4:STAR(7)
2 <xf> <x> | 7: CLOSE1(9)
2 <xf> <x> | 9: END(0)
Match successful!
matched (f*?) of "", starting at offset of 2, ending at pos of 2
Matching REx " (f*?) " against "x"
2 <xf> <x> | 1:OPEN1(3)
2 <xf> <x> | 3:MINMOD(4)
2 <xf> <x> | 4:STAR(7)
2 <xf> <x> | 7: CLOSE1(9)
2 <xf> <x> | 9: END(0)
Match possible, but length=0 is smaller than requested=1, failing!
EXACT <f> can match 0 times out of 1
+...
failed...
3 <xfx> <> | 1:OPEN1(3)
3 <xfx> <> | 3:MINMOD(4)
3 <xfx> <> | 4:STAR(7)
3 <xfx> <> | 7: CLOSE1(9)
3 <xfx> <> | 9: END(0)
Match successful!
matched (f*?) of "", starting at offset of 3, ending at pos of 3
Matching REx " (f*?) " against ""
3 <xfx> <> | 1:OPEN1(3)
3 <xfx> <> | 3:MINMOD(4)
3 <xfx> <> | 4:STAR(7)
3 <xfx> <> | 7: CLOSE1(9)
3 <xfx> <> | 9: END(0)
Match possible, but length=0 is smaller than requested=1, failing!
EXACT <f> can match 0 times out of 1
+...
failed...
Match failed
Freeing REx: " (f*?) "
Do you see?
Match possible, but length=0 is smaller than requested=1, failing!
($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
