> -----Original Message----- > From: Joe Sprankle [mailto:[EMAIL PROTECTED]] > Sent: Wednesday, July 31, 2002 1:44 PM > To: [EMAIL PROTECTED] > Subject: more regex woes... > > > Hi all, > I am brand new to perl, and programming at that. I'm learning > alot from > Robert's Perl Tutorial and I was hoping someone culd possibly > clear up the > following from the tutorial:
What is "Robert's Perl Tutorial"? > > $_='My email address is <[EMAIL PROTECTED]>.'; > print "Match 1 worked :$1:" if /(<*)/i; > > $_='<My email address is <[EMAIL PROTECTED]>.'; > print "Match 2 worked :$1:" if /(<*)/i; > > $_='My email address is <[EMAIL PROTECTED]<<<<>.'; > print "Match 3 worked :$1:" if /(<*>)/i; > > Match 1 is true. It doesn't return anything, but it is true > because there are 0 < at the very > start of the string. > Match 2 works. After the 0 < at the start of the string, > there is 1 < so the > regex can match that too. > Match 3 works. After the failing on the first < , it jumps to > the second. > After that, there are plenty more to match right up until the required > ending. > I've been doing fine so far but I just can't seem to > completly grasp this > part. What don't you understand? Why they capture what they do? They all capture the leftmost, longest substring matching the pattern. An regex like /<*/ will *always* match at the beginning of the string, since '*' means "zero or more of the preceding item". So this regex will only capture <'s if they appear at the beginning of the string. Perhaps that's what "Robert" is trying to illustrate. The regex /<*>/ won't necessarily match at the beginning, because the zero or more <'s must be followed by one > char. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
