If you provide a data sample (good), try to make sure that it should return some values with your test code -> you can't match 'RTVs' if all the subject headers are 'Fw: Hey Ugly line expansion and re-offer'.

As was mentioned on CB earlier, try creating a hash to avoid duplicates. Specifically, with an array of arrays named @array,

%test_hash = ();
for (@array) {
    if (exists ($test_hash{$_->[10]})) {next}
    print @{$_};
    $test_hash{$_->[10]} = 1;
}
[download]

Update:As per an OP request, here's melding the above code with his posted code.

my %test_hash = ();
while (my $cols = $csv->getline($fh)) {
    last unless @$cols;
    next unless defined $cols->[$column_to_search]
            and $cols->[$column_to_search] eq $wanted_value;
    if (exists ($test_hash{$cols->[10]})) {next}
    $test_hash{$cols->[10]} = 1;
    for (0,1,7) {
        $cols->[$_] = '' unless defined $cols->[$_];
    }
    print join(' ',$cols->[0],$cols->[1],$cols->[7],$cols->[9],$cols->
+[13],$cols->[18],$cols->[19]),"\n";
}
[download]