in reply to greedy search

$str = 'aaaaa';
$str =~ s/a+/b/;

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Since '+' is greedy, you end up with 'b' in $str.
If '+' wasn't greedy, you'd end up with 'baaaa' in $str.

You can make '+' non-greedy by following it with a '?':

$str1 = $str2 = '111b222c333c444';
$str1 =~ s/b.+c//;
# $str1 contains '111444'.
$str2 =~ s/b.+?c//;
# $str2 contains ''111333c444'.

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'*' and '?' can similarly be modified with a '?'.

Both greedy and non-greedy are useful. Use whichever one you need in a particular situation.

Replies are listed 'Best First'.
Re^2: greedy search
by monarch (Priest) on Jun 03, 2005 at 05:45 UTC
    Searches are greedy by default. But one situation where you want a non-greedy search that is fairly common is finding the contents of an HTML tag.

    Let's say you have:

      <a href="?"><b>Hello</b></a>

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    If you pattern match using /<(.+)>/ your match will contain "a href="?"><b>Hello</b></a".

    If you pattern match using /<(.+?)>/ your match will contain "a href="?"", which is usually what people are looking for.

    Having the option is great, more power in your hands to find what you want!

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