For C/C++ ocde you can also have a look at SWIG, the Simplified Wrapper and Interface Generator. Of course, using XS is also an option, some information can be found in Advanced Perl Programming by Simon Cozens (and probably elsewhere, but that's what I used).

Apart from the Inline::Java module mentioned above there's also Java which allows a Perl program to access a local or remote JVM.

Hope this helps, -gjb-