I did a little playing with this, to try to learn something. 
%h = (1 => 2, a=>"b", c => 2);
%h = reverse (%x = reverse %h); 
foreach my $n (keys %h) {
  print "$n $h{$n}\n";
}

[download]
Yeah, I know. Anyway, here's what I get: 
 2
1 2
a b

[download]
As if a duplicate element were eliminated by making the key null. But if I do 
%h = (1 => 2, a=>"b", c => 2);
%x = reverse %h;
%h = reverse %x; 
foreach my $n (keys %h) {
  print "$n $h{$n}\n";
}

[download]
I get 
1 2
a b

[download]
which is what I'd expect. Now, here's yet another thing: if I create another duplicate, d => 2 (at the end of the list), I still get the same end result; that duplicate is eliminated. In fact, in the first bit of code, I still get three lines of output. If there are duplicates, it doesn't seem to be guaranteed which one is eliminated by the reverse. I just looked at reverse in my Camel book and it doesn't mention anything about duplicates, so I suspect the order can't be relied upon. Typical for a hash.

In reply to Re: whats wrong reverse %x = reverse %h? by melora
in thread whats wrong reverse %x = reverse %h? by borisz

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