Just the Perian plug-in won't get you anywhere. Get the free MPEG Streamclip program to play and convert .flv files and many others (the Perian plug-in is still needed).
I've been experimenting with this as well. I have found imovie HD (free download) will allow you to import .flv files just fine. I don't understand why imovie (a newer version) doesn't have the same capability. Beyond my pay grade.
This thread has been closed by the system or the community team.
You may vote for any posts you find helpful, or search the Community for additional answers.
Import FLV into iMovie
Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.