How 'bout a hash of hashes, step through them with a nested for loop (code untested)?

my %outer = ();
$outer{object1}->{object1} = 78;
$outer{object1}->{object2} = 45;
...
$outer{object2}->{object4} = 13;
foreach my $outer_key (sort keys %outer) {
  print $outer_key, "\t";
  foreach (sort keys %{$outer{$outer_key}}) {
    print $outer{$outer_key}->{$_}, "\t";
  }
  print "\n"
}
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Update Man! A monk sure has to be quick to beat out the PonyMaster.

Another Update: Note that Albannach's solution below is better, since it allows for holes in the inner hash.