Re: Dynamic variable scoping

[Allison Randal]

If the problem is simply "implement Common Lisp special variables", then 
the most likely solution is to create a LispSpecialVar PMC. In the same 
way that a MultiSub acts like a sub but internally stores a list of 
subs, the LispSpecialVar would act like an ordinary variable to Parrot 
internals and to all other languages, but would internally store a stack 
of previous dynamic bindings.

Likewise, the behavior at the point when a PMC is shared across threads 
is determined by the 'share' and 'share_ro' vtable functions, and so 
easily implemented within a LispSpecialVar PMC.

Allison