Well, one way of doing it is with building indexes that contain references to the specified structures. Something like:

my %company_phone_index = (
     'company' => "ABC Co.",
     'phone' => "+1-888-123-4567",
     'structs' => [ $company_one_ref, $company_two_ref ]
);
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Atleast that should give you an idea. Note, you will have to handle the maintenance of the data (i.e. the company $company_one_ref closed down).

Another method would be to put the structure into a database and create indexes on the desired traits so you can retrieve the 'groupings' of like data quickly.

I would make some changes to your structures - namely, I'd abandon most of the arrays and use hashes. %domains would be a HoH where the lower-level H has the same keys as %data. This reduces a dependancy on data order which makes things clearer for me. Ignore this if you want.

%data would become a HoHoA. For convenience and some sort of standardisation, I would have the outter key be lt the inner key. For example, $data{address}{company} would exist, but $data{company}{address} would not, although $data{company}{fax} would exist. Then it's just a matter of putting all your data in all appropriate buckets, and then finding which inner arrayrefs have more than one domain in them.

There shouldn't be much memory usage here - just lots of refs.

This sounds like it's related to Metric for confidence of complex match? Did that not work out, or did the specification change?

That part worked fine, this is just a different way of handling the same data. It was much simpler than I thought it would be.

---

Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

use strict;
use warnings;

my (%domains, @domains, @sets, $i, $j);

%domains = (
    'domain1.com' =>
        ['company1', 'contact1', 'address1', 'phone1', 'fax1', 'email1
+'],
    'domain2.com' =>
        ['company2', 'contact2', 'address2', 'phone1', 'fax2', 'email1
+'],
    'domain3.com' =>
        ['company3', 'contact3', 'address3', 'phone3', 'fax3', 'email3
+'],
    'domain4.com' =>
        ['company3', 'contact4', 'address4', 'phone3', 'fax1', 'email1
+'],
    'domain5.com' =>
        ['company5', 'contact5', 'address5', 'phone5', 'fax5', 'email5
+'],
    'domain6.com' =>
        ['company5', 'contact6', 'address6', 'phone6', 'fax6', 'email5
+']);

@domains = keys %domains;
while ($#domains > -1) {
    my @newset = shift @domains;
    for ($i = 0; $i <= $#newset; $i++) {
        for ($j = 0; $j <= $#domains; $j++) {
            push @newset, splice(@domains, $j--, 1)
                if compare($newset[$i], $domains[$j]);
        }
    }
    push @sets, \@newset;
}

for (@sets) {
    print join ' ', sort @$_; print "\n";
}

sub compare {
    my $d1 = $domains{$_[0]};
    my $d2 = $domains{$_[1]};
    my $c = 0;
    for (0..$#$d1) {
        return 1 if $d1->[$_] && $d1->[$_] eq $d2->[$_] && ++$c == 2;
    }
}
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#!/usr/bin/perl -w

use strict;
use Data::Dumper;
use Digest::MD5 qw(md5_hex);

# I want to group domains together if they share at least two of those
+ values.
# The 1st two entires match, the 3rd not
my %domains = (
               'foo.com' => {
                           phone => '1234',
                           company => 'big co',
                           contact => 'john',
                           address => 'cool street',
                           fax     => '5678',
                           email   => 'john@bigco.com',
                          },
               'bar.com' => {
                           phone   => '2222',
                           company => 'small co',
                           contact => 'jeff',
                           address => 'bad street',
                           fax     => '5678',
                           email   => 'john@bigco.com',
                          },
               'baz.com' => {
                           phone   => '9999',
                           company => 'another co',
                           contact => 'judy',
                           address => 'nasty street',
                           fax     => '8888',
                           email   => 'frank@anotherco.com',
                          },
              );

# Build permutation hash
foreach my $domain (keys %domains) {

    # Iterate over all the elements in the domain hash
    foreach my $o_attr (keys %{$domains{$domain}}){

        # As we're creating hashes of each permutation we need to iter
+ate
        # over the same elements
        foreach my $i_attr (keys %{$domains{$domain}}){

            $domains{$domain}{hash}{$o_attr}{$i_attr} = md5_hex(${$dom
+ains{$domain}}{$o_attr}.${$domains{$domain}}{$i_attr});

        }
    }

}

print Dumper(%domains);
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You can then loop over all the permutations looking for hashes that match!