# get date 90 days ago
my ($start_d, $start_m, $start_y)
  = (localtime(time - 90 * 86_400))[3,4,5];

my $start = sprintf('%4d-%02d-%02d', $start_y+1900, 
                                     $start_m+1,
                                     $start_d);

foreach (<FILE>) {
  my ($y, $m, $d) = (split /,/)[28,29,30];

  my $date = sprintf('%4d-%02d-%02d', $y+1900, $m+1, $d);

  if ($start gt $date) {
    # record is more than 90 days old
  } else {
    # record is within 90 days
  }
}