So, in this case the code I posted first works fine, right? What I am confused about is why you want to pass things like this:

my_sub(\%hash);
[download]

instead of like this:

my_sub(%hash);
[download]

But, it really doesn't matter, if the solution works for you just use it :)

Hrm, do you want the changes to be cumulative or to reset each time?