You need to read the documentation on this and understand it:

https://www.varnish-cache.org/docs/4.0/whats-new/index.html

Otherwise you should just be using a popular file from around the web. Take a look at the Varnish Utilities Directory:

https://www.varnish-cache.org/utilities

There you can find two of the best resources for ready to go VCL (for now Varnish 3 only):

https://github.com/slashsBin/nuCache

https://github.com/mattiasgeniar/varnish-3.0-configuration-t...

I am sure that if you ask nicely, the project members of these efforts might just give you a hand and upgrade to VCL 4.0 syntax a usable Wordpress template. Be willing to test and contribute back with whatever you can though.