Previously the expression operations happened right-to-left so `1 - 2 - 3 - 4 - 5` was actually calculated as `(1 - (2 - (3 - (4 - (5)))))`. Now the expressions are calculated according to BODMAS, with boolean expressions calculated last.
Instead of creating a new Vec<_> for every embedded path part, we now use a reference when calling get/set/del on a value’s data. This means we aren’t creating and copying the Vec items each and every time we traverse down a path.
