How to implement lexical closures?

I'm working on a toy interpreter (http://code.google.com/p/zemscript/)
and trying to implement lexical closures (http://code.google.com/p/
zemscript/source/browse/#svn/branches/lexical_scope) . Currently when
the function is created it copies the symbol table. So the following
code works:
newCounter = function() {
        i = 0;
        return function() {
                i = i + 1;
                return i;
        };
};


c1 = newCounter();
c2 = newCounter();
println(c1() ~ " == 1");
println(c1() ~ " == 2");
println(c2() ~ " == 1");
println(c1() ~ " == 3");
println(c2() ~ " == 2");


However since it copies the symbol table the following does *not*
work:
create = function() {
        x = 0;
        return {
                "get" : function() { return x; },
                "set" : function(v) { x = v; }
        };
};


o = create();
o["set"](42);
println(o["get"]()); // Should print 42


What I can't work out is how I can get the second example to work
without breaking the first example.


Ant build file: http://pastebin.com/qDaZethE

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