The module solution would probably work fine (assuming my client can figure out how to install the proper module), but the other post seems a bit confusing. It doesn't matter though - I finally figured out how to do it properly with references (or is it pointers?):

use strict;
use warnings;

my %hash;
assign(\%hash, 'aa', 'bb', 'cc', 'value');
print $hash{aa}{bb}{cc};

sub assign {
    my $p = shift;
    my $val = pop;
    my $last = pop;
    for (@_) {
        $p->{$_} = {} if !$p->{$_};
        $p = $p->{$_};
    }
    $p->{$last} = $val;
}
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It came to me while I was lying in bed reading a book. Odd how that works.