$ cat hack_self.imc
.include "datatypes.pasm"

.sub _main
        new $P1, .PerlArray
        push $P1, .DATATYPE_INTVAL
        push $P1, 32
        push $P1, 0
        push $P1, .DATATYPE_FLOATVAL
        push $P1, 32
        push $P1, 0

         .sym pmc Nul
        null Nul
        getinterp P5
        dlfunc P0, Nul, "Parrot_UnManagedStruct_get_pointer", "pIP"
        invoke
        set $P2, P5
        assign $P2, $P1

        print I20
        print "\n"
        print N10
        print "\n"

        set $P2[0;20], 20
        set $P2[1;10], 42.0

        print I20
        print "\n"
        print N10
        print "\n"
        end
.end
$ parrot hack_self.imc
0
0.000000
20
42.000000

This is unlimited self-inspection and self-modification :) With little
additions (nested structs) one could read/write all Parrot_Interp
internals (including possible security bits) and not only registers like
above. But current state is already sufficient to seriously damage the
interpreter ($P2 above is a struct representing the current interpreter)

leo