>>15
There's nothing emulated here, but there is some confusion of terminology. Parameters are first class objects, which makes them more powerful than plain old dynamically scoped variables. But they are not exactly variables. If you need variables, have a look at how fluids are built in Guile or make your own with dynamic-wind and some binding macro to hide the magic. It's done in a few minutes.
(It's not an emulation if it's just a real implementation. Here we're not building a meta-level where the new thing is possible, we're just doing it on the same level as everything else.)