You know, quite apart from the problems you have with the non-interpolation of hashes (which others have explained to you), your code really doesn't do what you think it does.

$s="1 x 2 y";

This creates a scalar $s with the value "1 x 2 y".

@a = $s;

This creates an array @a that has one element. This one element has the value "1 x 2 y". I think you probably wanted to use split here.

%h = @a;

This creates a hash %h with one key, "1 x 2 y", and one value, undef. If you'd used split on the previous line then this would have created a hash with key/value pairs of 1 => x and 2 => y.

--
<http://www.dave.org.uk>

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg