Dans mon coeur en ta présence
Fleurissent des harengs saurs.
Ma santé, c’est ton absence,
Et quand tu parais, je sors.
I have kept the title, since a) I think it can be understood by English readers, and b) I couldn't better it! I don't think the merdrigal has become an established form, but perhaps it should...
Within my heart, when you are here,
Pickled herrings bloom.
My health is your absence; when you appear
I swiftly leave the room.