EASY: as2 / NOTEASY: as3? - SWF loads SWF, but how to pass params with caching?

I’m going crazy with this one.

I have a SWF loader and a SWF child that will be loaded into it.

How can I load the child, and pass it a parameter?

This seems like a simple question, but I cannot find the answer. The only solution I have seen is to pass the parameter in the URL, but then that ruins caching of the SWF child.

In AS2 this was easy. I could use FlashVars.

There has to be a way to do this in AS3. (Also, I have no control over the SWF child, so I cannot put special methods in there or anything. I can just tell them to expect a parameter to be passed somehow for them to use.)

Thanks!

p.s. I saw the other thread. But, it seems like they want something else possibly, and no solution was found.