%HASH in scalar context reveals C<"1/16">, which means only one out
of sixteen buckets has been touched, and presumably contains all
10,000 of your items. This isn't supposed to happen. If a tied hash
-is evaluated in scalar context, a fatal error will result, since this
-bucket usage information is currently not available for tied hashes.
+is evaluated in scalar context, the C<SCALAR> method is called (with a
+fallback to C<FIRSTKEY>).
X<hash, scalar context> X<hash, bucket> X<bucket>
You can preallocate space for a hash by assigning to the keys() function.