Examples on how to purge the cache in Varnish.

purge.vcl

vcl 4.0;

sub vcl_recv {
    // Allow PURGE requests to remove a specific object if it exists.
    if (req.method == "PURGE") {
        return (purge);
    }

    // Allow BAN requests, adding a lurker friendly ban to the ban list.
    if (req.method == "BAN") {
        ban ("obj.http.X-Ban-Host == " + req.http.Host + " && obj.http.X-Ban-Url == " + req.url);
        return (synth(200)); 
    }

    // Allow REFRESH requests to update cached objects.
    if (req.method == "REFRESH") {
        req.hash_always_miss = true;
    }
}

sub vcl_backend_response {
    // Attach ban related headers to the cache object.
    set beresp.http.X-Ban-Host = bereq.http.Host;
    set beresp.http.X-Ban-Url = bereq.url;
}

sub vcl_deliver {
    // Remove debug and logic headers.
    unset resp.http.X-Ban-Host;
    unset resp.http.X-Ban-Url;
}