my @pairs = split /&/, $query_string;
foreach my $p(@pairs) {
    $p =~ tr/+/ /;
    $p =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
    my ($key, $val) = split /=/, $p, 2;
    $data{$key} = $val;
}