Well, you could do

my $iter = get_value_iter($oWkBook);
while ($iter->(my $item)) {
   print("$item\n");
}
[download]

if you defined get_value_iter as follows:

sub get_value_iter {
   my @values = @_;
   my $sub_iter;

   return sub {
      our $rv; local *rv = \$_[0];

      for (;;) {
         if ($sub_iter) {
            if ($sub_iter->($rv)) {
               return 1;
            }

            undef $sub_iter;
         }

         return if not @values;

         $rv = shift(@values);

         while (ref($rv) eq 'SCALAR') {
            $rv = $$rv;
         }

         if (ref($rv) eq 'ARRAY') {
            $sub_iter = get_value_iter(@$rv);
            next;
         }

         if (ref($rv) eq 'HASH') {
            $sub_iter = get_value_iter(values %$rv);
            next;
         }

         return 1;
      }
   };
}
[download]

Scalar::Util's reftype can be used instead of ref if you wish to traverse objects.