#!/usr/bin/perl
use strict;
use warnings;
use Date::Simple qw/ today /;

my $yesterday = today() - 1;
my $wk_before = $yesterday - 7;
for ($yesterday, $wk_before) {
	$_ = $_->strftime('%Y%m%d');	
}

while (<DATA>) {
	print if $_ ge $wk_before && $_ le $yesterday;
}

__DATA__
20110801-23:42:01,4
20110802-23:42:01,4
20110802-23:45:01,3
20110802-23:48:01,1
20110802-23:51:01,1
20110802-23:54:01,2
20110802-23:57:01,3
20110803-00:00:01,3
20110810-23:42:01,4