The split with parenthesis: () captures the elements within. You might perhaps be able to better appreciate the difference by looking at an alternate form of the same expression and operation as given below: (please notice the presence and absence of () in the split commands.

#!/usr/bin/perl

 

use strict;

use warnings;



my $x = '12aba34ba5';

my @num = split/[a-b,A-Z]/, $x;

print "$num[$_],\n" foreach (0..$#num);

print"-------\n";

@num = split/([a-b,A-Z])/, $x;

print "$num[$_],\n" foreach (0..$#num);
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Update: the (?:) makes sure that this is not captured so if you try out:

@num = split/(?:[a-b,A-Z])/, $x;

print "$num[$_],\n" foreach (0..$#num);
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it will spit out the same output as:

@num = split/[a-b,A-Z]/, $x;
print "$num[$_],\n" foreach (0..$#num);
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(apologies for the length of this reply).