Nginx syntax problem '~*'

I have at condition checking to see if user has a cookie like this:

 if ($http_cookie ~* "developer=true" ) {
   ...
 }

I'm not familiar with the ~* syntax, I assume that that means if it 'contains', but what about the opposite? like what if I wanted to check if $http_cookie doesn't contain that cookie?

From stackoverflow

• You can test the variable does not match a regex using !~ (case sensitive) and !~* (case-insensitive) operators:

  if ($http_cookie !~* "developer=true") {
  }
  

  By the way, if you want to test a value of cookie named "developer", it would be probably more clear to say:

  if ($cookie_developer = "true") {
  }