while (my $row = $sth->fetchrow_hashref) {
   for my $db (@{$where{NEW_DB}}) {
      $row->{Db} = $db;
      for my $user (@{$where{NEW_USER}}) {
         $row->{User} = $user;
         print "INSERT INTO DB ";
         print join(",", map { "$_:'$row->{$_}'" } keys %{$row});
         print ";\n";
      }
   }
}