for my $d (sort {$a cmp $b} keys %{{map {$_ => $hash{$_}{desc}} keys %
+hash}} ) {
   ...
   ...
}
[download]

is unreadable. It should be

my %descs = map { $_ => $hash{$_}{desc} } keys %hash;

for my $d ( sort keys %descs ) {
   ...
   ...
}
[download]

The answer to your answer is now obvious.

my %descs = map { $_ => $hash{$_}{desc} } keys %hash;

for my $d ( sort { $descs{$a} cmp $descs{$b} } keys %desc ) {
   ...
   ...
}
[download]

Update: On the other hand, why are you building a hash at all??

my %descs = map { $_ => $hash{$_}{desc} } keys %hash;

for my $d ( sort { $descs{$a} cmp $descs{$b} } keys %descs ) {
   my $desc = $descs{$d};
   ...
}
[download]

can be written as

for my $d ( sort { $hash{$a}{desc} cmp $hash{$b}{desc} } keys %hash ) 
+{
   my $desc = $hash{desc}{$d};
   ...
}
[download]