@a = ( 1, 2, 3, 4 );
%h = @a;
print $h{1}; # prints 2
print $h{3}; # prints 4
print $h{2}; # prints nothing (undefined hash element)

@b = %h;
print $b[2]; # Unknown, since the hash doesn't maintain order
             # Exact behavior is undefined, and often 
             # changes between perl versions.

$ref = { @a }; # $ref gets a hash ref, but the anonoymous ref
               # is built with an array.