I wanted a regex to match milestone version numbers where the version number could have two or three numbers and an optional milestone suffix. The following test code partially works:

for my $entry (qw(1_0 1_0_1 1_0_beta 1_0_1_beta)) {
    print "$entry\n" if $entry =~ /^\d+ _\d+ (?> (?:_\d+)? \w+) $/x;
}

[download]

Prints:

1_0_1
1_0_beta
1_0_1_beta

[download]

The 1_0_1 is unexpected (and unwanted). I would have thought the no backtracking section should prevent matching the trailing _1 because (?:_\d+) would match and the backtracking suppression would then cause the \w+ part of the match to fail. What have I misunderstood?

True laziness is hard work

In reply to Unexpected regular expression match by GrandFather

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