Just realised that you want to port that to C eventually so below is no good. I would just use ikegami's - don't forget to free.

You want to separate even/odd: here are 2 variations on tybalt89's which do retain the even matches as well as the odd. Assuming your system can take it:

use strict;
use warnings;

# trivial variation on tybalt89's to retain
# both odd and even one after the other
my $sample = "041424344454647484940414";
my @allin = $sample =~ /(\d)(\d)/g;

# more ordered output using subs in regex
my @odds_vs_evens = ();
$sample =~ s/(\d)(\d)/push(@odds_vs_evens,[$1,$2])/eg;

print $_->[0].'->'.$_->[1]."\n" for @odds_vs_evens;
[download]

0->4
1->4
2->4
3->4
4->4
5->4
6->4
7->4
8->4
9->4
0->4
1->4
[download]

But this is what I was after:

my $sample = "041424344454647484940414";
my %odds_vs_evens = $sample =~ /(\d)(\d)/g;
[download]

Alas it is not ordered and the World just lost some more balance.

bw, bliako