If you have more data to return than an 'exit' would do, you could use named pipes (the caller creates the pipe and passes the name to the Perl program).

Still another possibility - provided that your Perl program does not use them otherwise - would be to have Perl output the return data to STDOUT or STDERR. I'm not so proficient with Java, but I guess there will be something equivalent to Perl's qx() in Java too...