Java is notorious for it's slow startup. If you execute java hepler for some web-applications from user requests, it could be performance killer for your application (e.g. as I think, if you run 10 java instances in simultaneously)

So, if you have access to java-sources and know java a little bit, to rewrite your helper as network daemon, listening local interface and communicate with it via sockets. At least problem with "startup overhead", which you attribute to perl, will disappear.