It's not too pretty, but you can use the baby-cart:

use strict;
use warnings;
use Storable;

my %h2;
my %hash = (

    'roster' => {
        'mike'  => 'biology',
        'carol' => 'math',
        'tom'   => 'history',
    },

    'courses' => {
        'math'    => 'full',
        'biology' => 'open',
        'art'     => 'open',
    }
);

store( \%hash, "test.dat" );
%h2 = %{ retrieve "test.dat" };

for ( sort keys %h2 ) {
    print "$_: @{[values %{$h2{$_}}]}\n";
}
[download]

Output:

courses: open full open
roster: history math biology
[download]

Hope this helps!