Re: Regex bug in 5.10 (was: Using Look-ahead and Look-behind)

[jds17]

You are right, my change did not affect greediness. The bad thing is: now I don't understand why my proposed solution worked at all. Maybe someone can explain? I don't think the question is too important, but I like to use regular expressions and it bugs me a little if I cannot understand one (especially such a tiny one).

I have read the documentation you have cited and it helped, so I played around some more and tried out the following, which only exchanges "+" for "*" in your original expression, really works as one would think and therefore would be my preferred solution, at least for Perl 5.10:

$_ = "Hello";
print "$1\n" while /(?=(.+))/g;

Output:

Hello
ello
llo
lo
o

[ikegami]

Note that using + instead * is not equivalent.

$ perl -e'$_ = "Hello"; print "<$1>\n" while /(?=(.*))/g;'
<Hello>
<ello>
<llo>
<lo>
<o>
<>

$ perl -e'$_ = "Hello"; print "<$1>\n" while /(?=(.+))/g;'
<Hello>
<ello>
<llo>
<lo>
<o>