using variable in string in Lighttpd

Hi I'm trying to do this:

 $HTTP["url"] =~ "/(开发者_StackOverflow中文版[^/?]+)$" {
    setenv.add-response-header = (
    "Content-Disposition" => "attachment; filename=$1"
    )
 }

but it did not replace $1 with what stored in the regex but just $1 characters.

I'm wondering if something like this is possible in lighttpd.

It seems like the search/replace with regex only works in those redirect syntaxes.

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I've found the answer. It has to be done through mod_magnet which binds LUA scripting over lighttpd config.