Why don't you just take advantage of auto-vivification to generate hash keys and returning the value from your subroutine?

Something like:

sub total {
  my ($N_NUM) = @_;

  # expression is obviously pseudo-code
  if ($N_NUM is in database) {
    return 'FOUND';
  }

  return 'NOT FOUND';
}

my %dblist;
$dblist{"$N_NUM"} = total($N_NUM);

foreach my $item (sort keys %dblist) {
  # print table row
  print $item;
  print $dblist{"$item"};
}
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(edit: didn't really understand the question the first time, and am still not sure if I understand it.)