if the following are true:

• Expression Stack at time t = [ [ ], [ [ entry key: value, ys ], rest ] ]
• Value Stack at time t = [ [ evaluated_value, [ evaluated_key, [ ] ] ], [ next_level, other_levels ] ]

then Value Stack at time (t + 1) = [ [ entry evaluated_key: evaluated_value, next_level ], other_levels ]