use DateTime;

use strict;
use warnings;

my $oneweekago = DateTime->now()->subtract(days => 7)->strftime("%Y%m%d");

while (<DATA>) {
	print if /(\d{8})/ && $1 > $oneweekago;
}

=prints
abcd3.20110509-2345
=cut

__DATA__
abcd1.20110429-2345
abcd2.20110502-2345
abcd3.20110505-2345
abcd3.20110509-2345