> Thus Perl allows such constructs, by forcefully breaking the infinite loop.
Thanks, that wasn't clear to me.
BUT I should have taken more care about the
> WARNING: Difficult material (and prose) ahead. This section needs a rewrite.
FWIW, the forced break can be seen with re 'debug'
D:\tmp>perl -Mre=debug -e"'foo' =~ m{ ( o? )* }x;"
Compiling REx " ( o? )* "
Final program:
1: CURLYX[0]{0,INFTY} (12)
3: OPEN1 (5)
5: CURLY{0,1} (9)
7: EXACT <o> (0)
9: CLOSE1 (11)
11: WHILEM[1/1] (0)
12: NOTHING (13)
13: END (0)
minlen 0
Matching REx " ( o? )* " against "foo"
0 <> <foo> | 0| 1:CURLYX[0]{0,INFTY}(12)
0 <> <foo> | 1| 11:WHILEM[1/1](0)
| 1| WHILEM: matched 0 out of 0..65535
0 <> <foo> | 2| 3:OPEN1(5)
0 <> <foo> | 2| 5:CURLY{0,1}(9)
| 2| EXACT <o> can match 0 times out
+of 1...
0 <> <foo> | 3| 9:CLOSE1(11)
0 <> <foo> | 3| 11:WHILEM[1/1](0)
| 3| WHILEM: matched 1 out of 0..655
+35
| 3| WHILEM: empty match detected, t
+rying continuation... <---- HERE
+
0 <> <foo> | 4| 12:NOTHING(13)
0 <> <foo> | 4| 13:END(0)
Match successful!
Freeing REx: " ( o? )* "
D:\tmp>
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