my %h = %$ptr;

##</code><code>##

 my @a = $h{'stack'};

##</code><code>##

  local *h=$ptr;  # %h now is synonymous with %debug
  local *a=\$h{stack};  # @a is another name for the anon array @{ $h{stack} }
  # Now, a 'push' into @a will change %debug