There are a number of approaches you can take to store multi-valued hashes to disk. You mention "tie" so i will assume you want to tie a file, i.e. you want to be able to treat the stored hash as a normal hash. The MLDBM module mentioned by karlgoethebier allows you to store multi-level hashes by serializing the values and is very flexible.

If your values always follow the same format (i.e. are not arbitrary) then you can use DB_File or the more advanced BerkeleyDB directly and install your own serialization methods via DBM filters. These filters are invoked transparently every time you read or write a value to the database.

If you can show a sample of your hash structure some other methods can be suggested.