Re: substring problem???

Using a regex is one way to do it:

use strict;
use warnings;

my $string = 'ABCDEFGHIJKLMNOPQ';
my $tail = 'OPQ';
my $preLen = 4;

if ($string =~ /(.{$preLen})$tail/) {
    print "$1\n";
}
[download]

Prints:

KLMN
[download]

DWIM is Perl's answer to Gödel

Comment on Re: substring problem??? Select or Download Code

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Re^2: substring problem??? by Limbic~Region (Chancellor) on May 28, 2006 at 15:49 UTC
GrandFather, The problem asked is far more interesting than the real problem actually desired (last 4 chars of a string). I would submit the following as a starting point for the asked problem: `my $desired = substr($string, index($string, $tail) - 4, 4);` [download] It has a few obvious flaws but since the desired problem isn't the one asked, I didn't pursue it. Cheers - L~R	[reply] [d/l]
Re^3: substring problem??? by davido (Cardinal) on May 28, 2006 at 16:02 UTC
I tinkered with that too, and then abandoned it simply because it seemed to require too much status checking. If $tail isn't found in $string, index returns a -1, so you've got to check for that. And then if index() - 4 doesn't exist, you have another problem that will generate a warning, so an out of bounds check needs to be performed as well. I suspect that the substr(..., index()) method is at least as speed efficient as the regexp approach, but it's definately more cumbersome to implement. I still like the substr/index approach for its straightforwardness, but regret the implementation will probably tend to look a little unPerlish. Dave	[reply]