why my reg ex matches greedy?

lngperl has asked for the wisdom of the Perl Monks concerning the following question:

Dear monks,

use strict;
use warnings;
my $str = '6AG3_608_FGG_20100124_20120923418_20126254447_201262512026.
+txt';
$str =~ m/(.*)(_\d{11,}?.*)(\.\w+)/;
print $1, "\n";
print $2, "\n";
print $3, "\n";
[download]

prints 6AG3_608_FGG_20100124_20120923418_20126254447
_201262512026
.txt

But i want it to print
6AG3_608_FGG_20100124
_20120923418_20126254447_201262512026
.txt

Basically the filename gets appened with "_timestamp" after the YYYMMDD part everytime when it gets processed. i want to strip out the time stamps alone.

What i am doing wrong here?

Any help is much appreciated and thanks.

Comment on why my reg ex matches greedy? Download Code

Replies are listed 'Best First'.
Re: why my reg ex matches greedy? by tobyink (Canon) on Jun 25, 2012 at 21:33 UTC
The `(.)` part is greedy because you've not used the ungreedy quantifier. The ungreedy version is `(.?)`. `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply] [d/l] [select]
Re: why my reg ex matches greedy? by McA (Priest) on Jun 25, 2012 at 20:44 UTC
Hi, probably that is what you want: `use strict; use warnings; my $str = '6AG3_608_FGG_20100124_20120923418_20126254447_201262512026. +txt'; $str =~ s/_\d{11,}//g; print $str, "\n";` [download]	[reply] [d/l]
Re^2: why my reg ex matches greedy? by Anonymous Monk on Jun 25, 2012 at 21:02 UTC
hi McA, thanks. yes that is what eventually i would need. but i would like to understand the reg ex to extract the pattern.	[reply]
Re^3: why my reg ex matches greedy? by McA (Priest) on Jun 25, 2012 at 21:12 UTC
Ok ok ok, then take this: `use strict; use warnings; my $str = '6AG3_608_FGG_20100124_20120923418_20126254447_201262512026. +txt'; $str =~ m/(.?)(_\d{11,}?.)(\.\w+)/; print $1, "\n"; print $2, "\n"; print $3, "\n";` [download]	[reply] [d/l]
Re: why my reg ex matches greedy? by roboticus (Chancellor) on Jun 25, 2012 at 20:19 UTC
Inperl: You can't just make up syntax and expect perl to know what you want. Read perlre, then read it a couple more times, then you should be able to figure out how to tell perl what you're looking for. ...roboticus When your only tool is a hammer, all problems look like your thumb.	[reply]
Re^2: why my reg ex matches greedy? by Anonymous Monk on Jun 25, 2012 at 20:56 UTC
i did not make my own syntax and expect perl to understand it. it is just that i do not know what i was doing wrong over there and trying to seek help.	[reply]
Re^3: why my reg ex matches greedy? by roboticus (Chancellor) on Jun 25, 2012 at 22:20 UTC
Well, clearly I'm an idiot. I thought I'd drop a mention of YAPE::Regex::Explain to show how to figure out what a regular expression is saying, so I could point out the "invented" bit. But I find that the bit I thought was "invented" seems fine. Sorry about that. When I run: `use YAPE::Regex::Explain; print YAPE::Regex::Explain->new(qr/(.)(_\d{11,}?.)(\.\w+)/)->explain +();` [download] I get: Read more... (3 kB) And I thought the `\d{11,}?` was the invented bit. I'll have to play with that sometime. ...roboticus When your only tool is a hammer, all problems look like your thumb.	[reply] [d/l] [select]
Re^4: why my reg ex matches greedy? by Anonymous Monk on Jun 26, 2012 at 04:53 UTC
Re^5: why my reg ex matches greedy? by roboticus (Chancellor) on Jun 26, 2012 at 12:14 UTC
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