Collecting snippets

So I'm generating some web pages and as I go through each page, I want
to record some keywords that depend on the content (related to whether
an IF or ELSE was processed, or the names processed in various lists
etc). The comes the kicker; I want the keywords to appear in a <meta>
element at the start of the page.

I'm sure there must be a way to do this, and I'm guessing it probably
involves WRAPPER, but my brain is fried. Can anybody give me a hint?

Thanks, Dave