If you must use a tied hash (which is slower and only allows you to order the keys one hash at a time) you should be aware of the fact that tied hashes don't act like normal hashes when used in boolean contexts.

my %hash
tie my %tied, 'Tie::IxHash';

$hash{foo} = 1; 
$tied{foo} = 1; 

print "hash is true\n" if %hash; 
print "tied is true\n" if %tied;    # Won't print.
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Until this is fixed, I think it's a good reason to avoid tied hashes when possible.

As for why does keys return in a pseudo-random order?
Its faster!

Or, more likely, it takes less space. Such a feature would probably be implemented with a separate array that holds the keys in order (which is basically how Tie::IxHash does it.)¹ With that strategy, returning them in order wouldn't be any faster, but storing them takes more space.

1. Tie::IxHash actually keeps both the data and the keys in arrays. It then keeps a hash of indexes. But, its the storage that grows, not the time to return the keys.

-sauoq
"My two cents aren't worth a dime.";