A good article on Regular Expression in Perl

I found a good one here: http://www.anaesthetist.com/mnm/perl/Findex.htm#regex.htm.
The author pointed out some very useful features of regex in Perl, especially on the "greedy" manner of Perl. He said, Perl will match as much the portion of text to the pattern as possible.
E.g :
regex=/a(.+)b/ and the string $s="axxbyyb"
What stored in $1 is "xxbyy" not "xx" cause it was matched greedily.
To obtain the minimum matched, which makes $1 to be "xx", we need to turn off the greedy behavior by /a(.+?)b/, i.e putting a ? afterward.

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