moritz is right, brute forcing this is straightforward, unless we've completely misunderstood the challenge. Here's my code which, with the data you gave, finds the split to be groups 0, 1, 4, 6 and 2, 3, 5, 7. (Machine numbers starting with zero). 
use strict;
use warnings;

my @costs;
push @costs, [split(/\s+/)] for (<DATA>);

my @combos;
gen_set([0..7],[],4,\@combos);
my $min_cost = 999999;
my $min_set_num;

for (0..$#combos) {
    my $set_cost = get_cost(@{$combos[$_]});
    if ($set_cost < $min_cost) {
        $min_cost = $set_cost;
        $min_set_num = $_;
    }
}

print "Set number $min_set_num, cost $min_cost: ".
  join(q{ },@{$combos[$min_set_num]}) . "\n";

sub get_cost {
    my @list = @_;
    my %list = map { $_ => 1 } @list;
    my $cost;
    for my $li (@list) {
        for my $oi (grep {not exists $list{$_}} (0..7)) {
            $cost += $costs[$li]->[$oi];
        }
    }
    return $cost;
}

sub gen_set {
    my ($from, $to, $num, $results) = @_;
    for my $item (@$from) {
        my @new_to = @$to;
        push @new_to, $item;
        if ($num == 1) {
            push @$results, \@new_to;
        } else {
            my @new_from = grep { $_ != $item } @$from;
            gen_set(\@new_from,\@new_to,$num-1,$results);
        }
    }
}


__DATA__
-  38 72 79 58 88 59 33
38 -  70 71 27 47 77 14
72 70 -  90 42 63 56 90
79 71 90 -  60 57 21 95
58 27 42 60 -  28 33 52
88 47 63 57 28 -  11 85
59 77 56 21 33 11 -  59
33 14 90 95 52 85 59 -

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In reply to Re: "Divide" challenge by bellaire
in thread "Divide" challenge by grizzley

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