How to block POST requests?

[Rt Ibmer]

>You can also use regular expressions for a bit more flexibility. This
>way you can explicitly accept only the request methods you allow and
>return the error code of your choosing.

>## Only allow GET and HEAD request methods
>      if ($request_method !~ ^(GET|HEAD)$ ) {
>         return 444;
>      }

Hello - I am using the latest nginx 6.  When I try to do as you say above I am getting the error in the nginx error file: unknown directive "if" in xyz.log

I am using your exact block as above and from your web page, like this:

  if ($request_method !~ ^(GET|HEAD)$ ) {
         return 444;
  }

I have tried this within the main server directive as well as from within location directives, but always get this error.  Obviously I am missing something? Thanks.