my $handle = $syb->prepare($query);
while(my @row = $select->fetchrow_array()) {
      # assuming that $row[0] is what you want to use in the
      # next query
      if($row[0] == 'ok') # it passes validation, yay 
      {
             $handle->execute($row[0]);
             # fetch all the rows here if you want
      }
      else {
             # this is how you trap errors, leave this blank if you wish
      }
}