This is how it would look with explicit labels and comefrom:

    puts("foo");
    before_defer0:
    comefrom after_defer1;
    puts("bar");
    after_defer0:
    comefrom before_defer0;
    puts("baz");
    before_defer1:
    comefrom before_ret;
    puts("qux");
    after_defer1:
    comefrom before_defer1;
    puts("corge");
    before_ret:
    comefrom after_defer0;
    return;

`defer` is obviously not implemented in this way, it will re-order the code to flow top-to-bottom and have fewer branches, but the control flow is effectively the same thing.

In theory a compiler could implement `comefrom` by re-ordering the basic blocks like `defer` does, so that the actual runtime evaluation of code is still top-to-bottom.