Build a hash of hashes (see perldsc) with the first hash keyed off the first column, the second level keyed off the second, and the value being the third. Then for each item in keys %hash print out the values for each of keys %{$hash{ $first }}.

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"
}

Update Man! A monk sure has to be quick to beat out the [Fletch|PonyMaster].

Another Update: Note that [Albannach]'s solution [node://565673|below] is better, since it allows for holes in the inner hash.

I noticed in your data there is no object2,object1 value in contradiction with your output sample, but with that in mind I'd elect to assume that not all cells in the table will necessarily be defined, and so you may need to inspect all the data to discover all the possible column names.

use strict;
use warnings;

my %table;
my %rows;
my %cols;

for() {
  my($row,$col,$val) = split ' ';
  $table{$row}{$col} = $val;
  $rows{$row}++;
  $cols{$col}++;
}

for my $col (sort keys %cols) {
  print "\t$col";
}
print "\n";

for my $row (sort keys %rows) {
  print "$row\t";
  for my $col (sort keys %cols) {
    print $table{$row}{$col} if defined $table{$row}{$col};
    print "\t";
  }
  print "\n";
}

__DATA__
object1 object1 78
object1 object2 45
object1 object3 34
object1 object4 45
object2 object2 89
object2 object3 32
object2 object4 13