I have a better understanding of your problem now, here's the code for my solution to problem #2. It's a bit hackish, but I thought I'd throw it out as one way to do it:

#!/usr/bin/perl -w

use strict;
use Data::Dumper;

my $seen = 0;

my @carmakers;
while (<DATA>) {
  chop;
  my ($id, $maker, $make) = split(",", $_);
  if ($id != $seen) {
    package block1;
    my %maker;
    $maker{'thismaker'} = $maker;
      my @makes;
      my %make = ('thismake' => $make);
      push(@makes, \%make);
    $maker{'makes'} = \@makes;
    push(@carmakers, \%maker);  # problem1
    $seen = $id;
  } else {
    package block2;
    my %make = ('thismake' => $make);
    push(@block1::makes, \%make);  # problem2
    $block1::maker{'makes'} = \@block1::makes;
  }
}

print Dumper( @carmakers );

__DATA__
1,gm,saturn
1,gm,chevy
1,gm,caddy
2,ford,taurus
2,ford,escort
3,vw,bug
3,vw,jetta
3,vw,phaeton
[download]

I'll think some more about problem 1, this is fun. :) Have you thought about a different way of structuring your database quer(y|ies)? For example, maybe you could use the database to get a unique set of carmakers.