If Java people go to Scala, C# go to F#, where do Ruby people go for functional nirvana?

I know a lot of Java people have started looking at Scala since it runs on the JVM, and a lot of people in the Microsoft world are looking at F#, but what does Ruby have as a natural functional successor?

In a pure FP sense Ruby doesn't lack anything, instead it has too much some may say. A functional language forces the programmer to not use global variables and other idioms so much (although it is possible to use globals in functional languages)