There's a good chance that replacing 1000 slow calls with one would help. I don't see any way of building a Perl hash, but you can return a list (using a "[]" return value) from which you can build the hash.

Using the above method, you'd still have to pass as many values as before. If that's the slow part, you could serialise the data for the hash into a single string on the Java side, then deserialise it on the Perl side. Then you only have one call, and only one value is exchanged between Java and Perl. This is of course far more complicated and error prone.

No guarantees.