my $dumper = Data::Dumper->new();
  $dumper->Terse(1);
  $dumper->Indent(0);

  my $sth = $dbh->prepare( 'SELECT * FROM table' );
  $sth->execute();

  # open a file to track all ids
  my $id_file_name = 'all-ids.txt';
  open my $id_fh, "> $id_file_name"
    or die "opening $id_file_name: $!"

  # array position of primary key
  my $id_ix = 0; 

  while ( my $cur = $sth->fetch() )
  {
      my $id = $cur->[$id_ix];
      open my $fh, "> $id"
        or { do warn "opening $id: $!"; next };
      print $fh $dumper->($cur);
      close $fh or warn "closing $id: $!";
      print $id_fh "$id\n";
  }

  close $id_fh
    or die "closing $id_file_name: $!";

  $sth->finish();