How wildcards works in Squid whitelisting configuration?

I'm a developer, not a sysadmin but I have the task to maintain a file which is basically a list of domains to whitelist. This file is used in the Squid caching proxy. The content of the file looks like this:

.example.com
.google.com
.bing.com

The file is used like this:

acl whitelist dstdomain "/path/to/squid/whitelist.txt"

Now I'm trying to find the documentation on how this file is parsed and I can't find clear (official) instructions on the Web on how to fill this file.

It seems that a dot before the domain will whitelist the domain and all it's subdomains. I'm trying to find if there is other wildcard rules that we can apply (like google.* or something like that).

I want to understand how it works not just follow blindly how we used this in the past.