Like this...

#!/usr/bin/perl

use strict;
use warnings;

my $date_time = qq(Sat, 05 Jan 2013 04:00:15 GMT);

$date_time =~ m/(.+), (\d{2} \w{3} \d{4}) (\d{2}:\d{2}:\d{2}) (\w+)/;

for ( $1, $2, $3, $4 ) { print qq($_\n) }

__END__

Karls-Mac-mini:monks karl$ ./dt.pl 
Sat
05 Jan 2013
04:00:15
GMT
[download]

$date_time =~ m/(.+), (.+) (.+) (.+)/;
[download]

Regards, Karl