split() behavior SOLVED

[gman]

Hello all,

I have a simple question regarding the behavior of split. Given a string following the pattern /w{2}.{4}/ I am getting an extra variable from split. I'm sure this is the correct behavior, I'm just not understanding why so can't correct it. see code:

#!/usr/bin/perl -w

use strict;
use Data::Dumper;


my $string = "df5434vg7856fg3472sd1234jh45r5";


my @array = split(/(\w{2}.{4})/,$string);

print Dumper(@array);

Output:

$VAR1 = '';
$VAR2 = 'df5434';
$VAR3 = '';
$VAR4 = 'vg7856';
$VAR5 = '';
$VAR6 = 'fg3472';
$VAR7 = '';
$VAR8 = 'sd1234';
$VAR9 = '';
$VAR10 = 'jh45r5';

Thanks in advance!

Thank You for the quick solution and explanation!

[BrowserUk]

Normally, split returns the bits either side of the delimiter, but not the delimiter itself. You've overridden that behaviour by adding capturing parens around the delimiter. Hence, it treats your input string as consisting of a sequence of null strings separated by 6 character delimiters which you've also asked it to capture:

(null)df5434(null)vg7856(null)fg3472(null)sd1234(null)jh45r5";

Basically, you're using the wrong tool for the job. m// does what you want:

print for "df5434vg7856fg3472sd1234jh45r5" =~ m[(\w{2}.{4})]g;;
df5434
vg7856
fg3472
sd1234
jh45r5

But actually, the most efficient way of breaking a string into fixed length fields is unpack:

print for unpack '(a6)*', "df5434vg7856fg3472sd1234jh45r5";;
df5434
vg7856
fg3472
sd1234
jh45r5

[PeterPeiGuo]

"If the PATTERN contains parentheses, additional list elements are created from each matching substring in the delimiter."

You can find the above in perldoc for split. There is also one example in the perldoc showing this behavior, you can check it out.