in reply to How do I refer to an element of a hash of arrays as an array

Since hash values can only be scalars, the value is a reference to an array. That is, it's like a pointer. (Try print "$h{'one'}\n" and see what you get.)

To get at the thing the reference points to, you need to explicitly dereference it. To get at the array, do

my @a = @{ $h{one} };
By enclosing something in the @{ } construction, you're saying that you want the array to which that reference points.