A lot of this list sounds very much like Postscript: * Code is stored in an array with the execute flag turned on. Therefore functions can be easily edited (or assembled) as data. First class functions all the way. * The environment is a dictionary (associative array), which can be swapped with another dictionary at any time (not just at function entry points). * Garbage collection is standard

I was thinking that it may be an interesting project to write a general purpose Postscript (non-graphics oriented) interpreter, with a decent library, full continuation passing support, a different way of handling the "current dictionary" stack (to allow for static in addition to dynamic variable support), and a swappable parser to allow for additional program definition styles (infix or prefix in addition to the default postfix notation). Just something kicking around in the back of my head for a while.