for my $row ( @{$serials}) {
        my $equ = $$row[$equIndex];
        my $pmf = $$row[$pmfIndex];
        my $pro = $$row[$proIndex];
        my $serial = $$row[$serialIndex];
        my $usr = $$row[$usrIndex];
        my $date = $$row[$dateIndex];
        my $clean = $$row[$cleanIndex];
        push @{$duplicates{$clean}}, [$equ, $pmf, $pro, $serial, $usr,
+ $date];
       }
    }
[download]

After the loop, check to see which hash entries have arrays with only one element