# Filter the query string to only include query
# parameters that are valid for your site
set req.url = querystring.filter_except(req.url,
  "query" querystring.filtersep()
  "page" querystring.filtersep()
  "foo"
);

# Sort the querystring params in alphabetical order
set req.url = querystring.sort(req.url);

# Lowercase specific query param values
set req.url = querystring.set(req.url, "query", std.tolower(subfield(req.url.qs, "query", "&")));
#set req.url = std.tolower(req.url); # (Or do this to lowercase the entire request URL)

# Remove headers that you want to avoid using to vary responses
unset req.http.user-agent;

# Normalise headers that you may vary on.  Accept-Language has a dedicated normalising function
set req.http.Accept-Language = accept.language_lookup("en:de:fr:nl", "de", req.http.Accept-Language);