Specifically, it supports native first class continuations, including both call/cc-style and delimited (shift/reset-style), which can form the basis for coroutines, generators, and other fun stuff. It also supports full tail call optimization.

Both of those features work with Java, Clojure, Scala, etc. For example: https://groups.google.com/d/msg/clojure/U4i4nVsYfi8/1GSGgNM8...

More info is available here: http://oss.readytalk.com/avian-web/javadoc-1.2.0/avian/Conti...