I maybe barking up the wrong tree, but I think I got your error. It took a bit of rooting around. Normally if the scalar is just a normal hash it should autovivify. Here is an autovivification example:

my $foo = { };
$foo->{a}->{b}->{c}->{d} = 1;
use Data::Dumper;
print Data::Dumper->Dump([$foo],['foo']);
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Results:

$foo = {
         'a' => {
                  'b' => {
                           'c' => {
                                    'd' => 1
                                  }
                         }
                }
       };
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All those keys were undef, but now they were created just by asking for them.

I got your error only when I tried to turn an undef into a hash reference explicitly:print %{$foo->{a}->{d}} So maybe making it into a two step process:

my $bar = $foo->{a}->{d};
print %$bar if $bar;
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that might take care of your errors. If I totally missed your problem, sorry.