As noted on the Perian site, development has ceased, and future versions may or may not continue to work. It seems with the upgrade to OS X 10.9 "Mavericks", the OS or Quick Look API has changed sufficiently that Perian no longer works.
Are there any alternatives? Ideally a one-app-does-all like Perian, but even a list of individual codecs and/or plug-ins for video container files would be useful.
NB: This question isn't about video players—there are many that support more than those playable via the built-in QuickTime player. This question is about codecs/plug-ins for QuickTime on OS X to allow it and Quick Look (and apps which rely on the OS to play videos) to open/play video files/formats lacking native support.