I understand that Perian is (a) not being developed by its creators anymore and (b) it doesn't work on 10.9/Mavericks even though someone appears to releasing updates to it on GitHub (gathering from trying Perian on 10.9, none of said updates seem to be related to 10.9 support).
I uninstalled this now apparently useless framework by clicking the Uninstall button in preferences, then removing the prefpane and rebooting.
The problem is that FLAC files still are read as a 'musical' MIME type - or something - by Finder. They have the preview music icon when they should be blank, but more confusing is that hovering over them gives a Play/Pause functionality which never actually plays anything (the icon just starts 'spinning' when you click it) Check the screenshot.
How do I get rid of this leftover broken functionality?
Also note: when I press space on a selected FLAC file, Quick Look correctly makes no attempt to play it - but Perian has left another annoying mark as QL throws up the musical notes icon - as if you could play it in QL):