$dbh=...
$sth->execute()
$sth->bind_columns(...)

t1= new Thread \&processor;
t2= new Thread \&processor;

t1->join();
t2->join();
#ends here#
sub hitMe { # :locked? 
   $sth->fetch();
   return (columns...);
}

sub processor {
   my $dbconn....
   my $dbh...

   while(@data=hitme()) {
     process stuff;
     $dbh->something();
   }
}