Duby: A Type-Inferred Ruby-Like JVM Language

Duby is an experimental project to create a JVM bytecode compiler for a 
Ruby-like language that infers static types from argument declarations 
and called methods. It is currently under development, but may eventually
be used to implement portions of JRuby, since Duby combines the terse,
neat syntax of Ruby with the performance of statically-typed Java 
bytecode. 

To compile the samples, run the following lines:

jruby lib/ruby/site_ruby/1.8/compiler/duby/compiler.rb <filename>

And to load and call them, use JRuby's Java integration:

CLASSPATH=. jruby -rjava -e "p Java::Foo.new.fib(35)"