Something is wrong with this pattern

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

Hello Monks,

I have strings in an array "@col" in all elements of this array there is one operator like "." or "+". Which is already stored in "$operator".

What i want is string on left & right side of the operator in each element of the array.

My code is like

foreach(@col){
        my $celldata=$_;
        $celldata=~s/<(set|x)?aln;(.*?)>//g;
        $celldata=~s/<(rct|rrt|rlt)?;(.*?)>//g;
        $celldata=~s/(<T(?:r|c)>)//g;
        #print "$celldata\n";
        if($celldata=~m{(.+?)$operator(.*)}){
            
            $left_str=$1;
            $right_str=$2;              print "$left_str === $operator
+ === $right_str\n";
}
}
[download]

Suppose @col contains elements like "2.2", "3.2", "1.3", "11.5" etc.. when i print left and right string for "11.5" it gives output as "1===.===.5". However I want "11===.===5"". I dont know what is wrong with the perticular pattern.

Can anybody please help me?

Thank you.

Comment on Something is wrong with this pattern Select or Download Code

Replies are listed 'Best First'.
Re: Something is wrong with this pattern by samarzone (Pilgrim) on Dec 24, 2010 at 06:55 UTC
The value inside `$operator` (supposed to "." in case of "11.5") is interpreted as special character inside regular expression. Escape its special meaning as following `$celldata=~m{(.+?)\Q$operator\E(.*)}` You can better use split for this if you have only one "`$operator`" in a string `($left_str, $right_str) = split(/\Q$operator\E/, $celldata);` -- Regards - Samar	[reply] [d/l] [select]
Re^2: Something is wrong with this pattern by tej (Scribe) on Dec 24, 2010 at 07:30 UTC
Thank you samarzone It is working fine now...	[reply]
Re: Something is wrong with this pattern by GrandFather (Saint) on Dec 24, 2010 at 06:34 UTC
What does $operator contain? As a general comment: .+? at the start or end of a regex will never match anything - don't do that. It's also good practise to use a character set in place of . when using * to avoid capturing more than you intend. True laziness is hard work	[reply]
Re^2: Something is wrong with this pattern by JavaFan (Canon) on Dec 24, 2010 at 10:34 UTC
As a general comment: .+? at the start or end of a regex will never match anything False: `$ perl -wE '"abcdef" =~ /(.+?)f/ and say $1' abcde` [download] Remember, "left-most match" trumps "shortest match".	[reply] [d/l]
Re^3: Something is wrong with this pattern by GrandFather (Saint) on Dec 24, 2010 at 21:42 UTC
Sigh, yes you are quite right and I didn't remember. Can we blame it on too much pre-Christmas cheer? Merry Christmas. ;) True laziness is hard work	[reply]