Beginner's Question: Understanding

Authoring Inform 7
1

Hi everyone, I’m an absolute beginner with Inform 7 and I wonder if someone could answer a quick question. I’ve been following a wikibooks tutorial that introduces understanding, so, for example:

Understand "toadstool" as the mushroom.

and simple conditions,

Understand "toadstool" as the mushroom when the mushroom is visible.

My question is, how do I make “toadstool” stand for mushroom ONLY AFTER the mushroom has been examined?
I.E. something like

Understand "toadstool" as mushroom when the player has examined the mushroom.

Or:

If the player examines the mushroom: understand "toadstool" as the mushroom.

Thanks in advance!

2 
Understand "toadstool" as mushroom when we have examined the mushroom.

Although I’m not sure that you really want to do this, as the player might want to use the word “toadstool” to mean the mushroom without having examined it.

3

Thanks. I had this working by setting a variable when the player examined the mushroom, but I knew there had to be a more elegant way. And yes, I understand your point; my motivation is really just about learning how things like this are done, without consideration of whether they should be done.