Need to use it with a call for the persistant variable to invoke the stored values. So test case works fine with

#!/usr/local/bin/perl -w
#
# name: persistest
#
# does stuff
# works fine

use vars qw( %hash );
use strict;
use Persistence 'test.dat';
[download]

persistent '%hash';

my ($k, $v, $n);
[download]

while

 (($k, $v) = each %hash) {
    $n++;
    print "$n: $k => $v\n";
}

%hash = ( blue => 'berries',
        red => 'roses',
        black => 'coffee',
        yellow => 'bananas',
        );

END { persistent '%hash'; }
[download]

The loop funniness was due to using foreach instead of while over the calls to each %hash.

Nothing to see here. Move along.