Further testing shows: it's actually not the read that blocks. It is the my $socket = IO::Socket::UNIX->new( Peer => $sockfile ); that never returns!

Is there a mechanism like the "Reuse" on file sockets as well? Is it possible some kind of lock lies on the file?

Even more testing shows: when the sock gets stale like this, even socat isn't able to connect to it (it doesn't complain but vlc doesn't react via the socket anymore)
Is this a vlc problem then?