this is actually what i finally came up with:

my ($key, $value, $len);
while (($key, $value) = each %HoL)
{
    my $href = $HoL{$key} = { map {$_, 1} @$value };
    do
    {
        $len = keys %$href;
        for (@HoL{@$value})
        {
            if    (ref eq "HASH" ) { @$href{keys %$_} = (1) x (keys %$
+_) }
            elsif (ref eq "ARRAY") { @$href{@$_} = (1) x @$_ }
        }
        $value = [ keys %$href ];
    }
    while (@$value > $len);
}
[download]

it's iterative no less. any comments?