Memcached - clear all keys matching a pattern?

I have some pages that serve up a massive tree of html, with a few
different varieties used on different pages. Generating the html is
quite intensive so I use memcached to store the different flavours,
generating a different key for each flavour.

When the tree contents change, i need to clear these keys out of
memcached so they will be re-generated next time someone goes to the
pages. So far i’ve been flushing everything with CACHE.flush
(CACHE.flush_all locally) but it would be better to just flush the
relevant keys. Since the key names are also subject to change, but all
contain the fragment “property_tree” in their names, ideally i would
like to drop all keys matching against /property_tree/ and leave the
rest.

Is there a way to do this? I can’t see any way of getting memcached to
tell me all of it’s saved keys.

thanks
max