nginx map with multiple capture groups results in `[emerg] unknown "a$b" variable`

Question

Is it possible to return multiple regex capture groups in a nginx map block?

This works fine, returning only the first capture group $a:

map $request_uri $result {
    "~(?<a>.)(?<b>.*)" $a;
    default $request_uri;
}

But I can’t return both capture groups as $a$b:

map $request_uri $result {
    "~(?<a>.)(?<b>.*)" $a$b;
    default $request_uri;
}

This causes a [emerg] unknown "a$b" variable error message when running nginx -t.

The same problem occurs if I use regular numbered regex capture groups ($1$2) instead of named capture groups.

Is there any way to do use a map to return multiple regex captures?

I'm using nginx 1.10.3.

Answer 1

I solved this thanks to @IvanShatsky. The solution is to upgrade nginx.

Versions of nginx before 1.11.0 do not support returning multiple capture groups. From the changlog:

Changes with nginx 1.11.0                                        24 May 2016

    *) Feature: the "map" directive supports combinations of multiple
       variables as resulting values.