Oh, if you get dizzy when authors write (_My stars! And you very well may!_) That white is black and that black is white, You should sit, quite still, in your chair and say:
Why it works
Noyes titles the poem "ENVOI" and opens with a direct address to the reader ("you"), enacting the envoi's defining function of "sending forth" the poem's closing wisdom to an external audience — the parenthetical aside (_My stars! / And you very well may!_) reinforces the intimate, dispatching tone of direct apostrophe characteristic of the form.