@mon = ('','Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec');

$_ = <DATA>; chomp;
$n{$_} = $c++ for split /\t/;

for (<DATA>) {
    chomp; split /\t/;

    @date = split /\//, $_[$n{'Date'}];
    $product = $_[$n{'Product'}];
    $country = $_[$n{'Imported_From'}];
    $quantity = $_[$n{'Quantity'}];

    $countries{$country} = () if !exists $countries{$country};
    $totals{$date[2]}{$date[0]}{$product}{$country} += $quantity;
}

@countries = sort keys %countries;

for (sort {$a <=> $b} keys %totals) {
    $year = $totals{$_};
    for (sort {$a <=> $b} keys %$year) {
        $month = $year->{$_};
        print "$mon[$_]\n";
        print join("\t", 'Product', @countries, 'Total'), "\n";
        for (sort keys %$month) {
            print;
            $product = $month->{$_};
            $total = 0;
            for (@countries) {
                print "\t".$product->{$_};
                $total += $product->{$_};
            }
            print "\t$total\n";
        }
        print "\n";
    }
}

__DATA__
Date	Product	Quantity	Imported_From
1/2/04	Shirts	32	Australia
1/9/04	Shoes	234	Asia
2/12/04	Caps	109	UK
4/4/04	Shoes	6	Asia
4/4/04	Shirts	12	Australia
5/6/04	Shirts	398	Australia