Currently you send a Content-Disposition header which tells the browser to download the file instead of playing it back:

print "Content-Disposition: attachment; filename=\"$name$ext\"\n";
[download]

Maybe removing the header is all you need. Does downloading the file work and produce a file identical to the original?

Also, I don't find any documentation for your choice of Content-Type: x-vlc-plugin. The only search results with that word are for example this Stackoverflow page, which talks about the client side HTML that is needed to embed the VLC plugin. Maybe using video/mp4 or audio/mp4 as the content type is the correct approach?

I would try to divide the problem into three parts:

1. Does the web server with your program send the file correctly?
2. Does your HTML page play a static file sent from the web server correctly?
3. If you have both parts above correctly, make your program send the same headers as the web server.