I think you've over complicated the example, the bug exists when using unevan or unordered parentheses.

Code:
var %() = Test1, %( = Test2, %) = Test3, %)( = Test4
echo -ag $eval(% $+ $chr(40) $+ $chr(41),1) = $eval(% $+ $chr(40) $+ $chr(41),2)
echo -ag $eval(% $+ $chr(40),1) = $eval(% $+ $chr(40),2)
echo -ag $eval(% $+ $chr(41),1) = $eval(% $+ $chr(41),2)
echo -ag $eval(% $+ $chr(41) $+ $chr(40),1) = $eval(% $+ $chr(41) $+ $chr(40),2)

To above would echo out:
Code:
%() = Test1
* Invalid format: $evalnext
%) = %
%)( = %

Albie