Suggestion to make the control flow more explicit

[brabalan]

In JSExplain, we only use let%ret for complex control flow, when several branches can continue with the same continuation.
Example: http://www.ecma-international.org/ecma-262/7.0/index.html#sec-validateandapplypropertydescriptor

• 1 always followed by 2
• if … then of 2 always return, else goes to 3
• if … then of 3 always return, else goes to 4
• if … then of 4 always return, else goes to 5
• else of 5 and else of 5.b go to 6

In our code, we should have an initial let%ref, a bunch of else if, and the in before step 6.

We could suggest to use this wording (start with else if if only one enter point in the control flow) for the spec.