# I assume this is already loaded up
my @AoA;

# lookback array
my @lookback;

my $lc = 0;
while (my $el = shift $AoA) {

   my $search = $el->[3];

   # see if search term in lookback
   if (grep("/$search/", map { $_->[3]}, @lookback)) {
     # found a match
   }

   if ($lc < 15) {
       $lc++;
   } else {
       # take 1 element off 
       shift @lookback;
   }
   push @lookback, $el;
}