Emacs support for Varnish's configuration language:
https://varnish-cache.org/docs/trunk/users-guide/vcl.html
This version of vcl-mode supports VCL-4.0.

The features provided are auto-indentation (based on CC-mode's
engine), keyword highlighting, and matching of {"..."} multi-line
string delimiters.

If you need support for VCL-2.0, you might have more luck with the older
package: https://github.com/ssm/elisp/blob/master/vcl-mode.el