Oh, Ok, you almost have it, @a = sort keys %{{a=>1,b=>2,c=>3}}; or in terms of your original problem, @a = sort keys %{{ map {$_ => undef} map {split} <> }}; Notice the replacement of parens with curlies. That makes the hashlike list into a hash reference to its contents, and the outer %{} dereferences it.

I agree with your desire to avoid temporary variables, I try to do that, too, in perl.