From the FAQ

Q: How does RPerl work?

A: The input to the RPerl compiler is low-magic Perl 5 source code. RPerl converts the low-magic Perl 5 source code into C++ source code using Perl and/or C++ data structures. Inline::CPP converts the C++ source code into XS source code. Perl's XS tools and a standard C++ compiler convert the XS source code into machine-readable binary code, which can be directly linked back into normal high-magic Perl 5 source code. The output of the RPerl compiler is fast-running binary code that is exactly equivalent to, and compatible with, the original low-magic Perl 5 source code input. The net effect is that RPerl compiles slow low-magic Perl 5 code into fast binary code, which can optionally be mixed back into high-magic Perl apps.

Now I remember Reini talking about it.

update

Though I'm not sure how the "mix back" is supposed to work.

IIRC from Reini's talk, something like Inline::Rperl is not intended.