$sevenDays = 60 * 60 * 24 * 7;
$now = time();
foreach $file ( @files ) {
    $mod_time = ( stat($file) )[9];
    if ( $now - $sevenDays < $mod_time ) {
        # Our file has been modified w/i last 7 days
    } else {
        # Hasn't been modified w/i last 7 days
    }
}