Parrot allows you to push all of the string registers (pointers, actually) and integer registers onto their own private stack with pushs, pushi and restore them with pops and popi. (Numerics and PMC's with n/p respectively.) So you *can* write recursive subroutines after a fashion but effectively you make the entire register set local to each recursion:

         set I0, 100
         bsr FUNC
         print I0     # Gives 100
         end
FUNC:    pushi
         set I0, 56
         popi
         ret
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local() for a particular registister can be emulated but it's a pain in the ass with something like:

         set I0, 100
         set I1, 200
         set I6, 700
         bsr FUNC
         # 
         print I0  # 100, original value
         print I1  # 0, new value
         print I6  # 0, new value
         end

         # Local changes to I1 and I6 preserved
         # think of this as unlocal()  :)
FUNC:    pushi   # saves all integer registers
         set I0, 0
         set I1, 0
         set I6, 0
         save I1
         save I6
         popi
         restore I6
         restore I1
         ret
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The answer to your other question (asked in /msg) is that no, you can't peer down the stack or get the stack's depth at this time. However you can simulate peering into the stack just fine with the tools given.