'aaaaaaaaaaaaaaa' =~ /^a+b/
####
'aaaaaaaaaaaaaaa' =~ /^a++b/
####
$ perl -Mre=debug -e'"aaaaaaaaaaaaaaa" =~ /^a+[bB]/'
...
Matching REx "^a+[bB]" against "aaaaaaaaaaaaaaa"
0 <> | 1:BOL(2)
0 <> | 2:PLUS(5)
EXACT can match 15 times out of 2147483647...
15 <> | 5: ANYOF[Bb][](16)
failed...
14 | 5: ANYOF[Bb][](16)
failed...
13 | 5: ANYOF[Bb][](16)
failed...
12 | 5: ANYOF[Bb][](16)
failed...
11 | 5: ANYOF[Bb][](16)
failed...
10 | 5: ANYOF[Bb][](16)
failed...
9 | 5: ANYOF[Bb][](16)
failed...
8 | 5: ANYOF[Bb][](16)
failed...
7 | 5: ANYOF[Bb][](16)
failed...
6 | 5: ANYOF[Bb][](16)
failed...
5 | 5: ANYOF[Bb][](16)
failed...
4 | 5: ANYOF[Bb][](16)
failed...
3 | 5: ANYOF[Bb][](16)
failed...
2 | 5: ANYOF[Bb][](16)
failed...
1 | 5: ANYOF[Bb][](16)
failed...
failed...
Match failed
...
$ perl -Mre=debug -e'"aaaaaaaaaaaaaaa" =~ /^a++[bB]/'
...
Matching REx "^a++[bB]" against "aaaaaaaaaaaaaaa"
0 <> | 1:BOL(2)
0 <> | 2:SUSPEND(9)
0 <> | 4: PLUS(7)
EXACT can match 15 times out of 2147483647...
15 <> | 7: SUCCEED(0)
subpattern success...
15 <> | 9:ANYOF[Bb][](20)
failed...
Match failed
...