Parrot virtual machine: I found this in this post about the future of Perl 6. Parrot is something like Java’s JVM or .Net’s CLR, but for multiple, dynamic, open-source languages.
Parrot is a register-based virtual machine being developed using the C programming language and intended to run dynamic languages efficiently. It uses just-in-time compilation for speed to reduce the interpretation overhead.
There’s discussion of having PHP, Puby, Python, and Perl compile down to Parrot, so you could have one part of your app written in Ruby that calls a function library written in some other language.