I 'am running Nginx with logging in debug mode and the report for "^/$" is :
2015/07/06 15:32:21 [debug] 6500#0: *9 accept: 193.137.170.139 fd:20
2015/07/06 15:32:21 [debug] 6500#0: *9 event timer add: 20: 60000:1436196801837
2015/07/06 15:32:21 [debug] 6500#0: *9 reusable connection: 1
2015/07/06 15:32:21 [debug] 6500#0: *9 epoll add event: fd:20 op:1 ev:80000001
2015/07/06 15:32:21 [debug] 6500#0: accept() not ready (11: Resource temporarily unavailable)
2015/07/06 15:32:21 [debug] 6500#0: *9 post event 0000000000AC5440
2015/07/06 15:32:21 [debug] 6500#0: *9 delete posted event 0000000000AC5440
2015/07/06 15:32:21 [debug] 6500#0: *9 http wait request handler
2015/07/06 15:32:21 [debug] 6500#0: *9 posix_memalign: 0000000000922D70:256 @16
2015/07/06 15:32:21 [debug] 6500#0: *9 malloc: 0000000000A450C0:1024
2015/07/06 15:32:21 [debug] 6500#0: *9 recv: fd:20 427 of 1024
2015/07/06 15:32:21 [debug] 6500#0: *9 reusable connection: 0
2015/07/06 15:32:21 [debug] 6500#0: *9 posix_memalign: 0000000000A46810:4096 @16
2015/07/06 15:32:21 [debug] 6500#0: *9 http process request line
2015/07/06 15:32:21 [debug] 6500#0: *9 http request line: "GET / HTTP/1.1"
2015/07/06 15:32:21 [debug] 6500#0: *9 http uri: "/"
2015/07/06 15:32:21 [debug] 6500#0: *9 http args: ""
2015/07/06 15:32:21 [debug] 6500#0: *9 http exten: ""
2015/07/06 15:32:21 [debug] 6500#0: *9 posix_memalign: 0000000000A47E10:4096 @16
2015/07/06 15:32:21 [debug] 6500#0: *9 http process request header line
2015/07/06 15:32:21 [debug] 6500#0: *9 http header: "Host: www.domain.com"
2015/07/06 15:32:21 [debug] 6500#0: *9 http header: "Accept-Encoding: gzip, deflate"
2015/07/06 15:32:21 [debug] 6500#0: *9 http header: "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"
2015/07/06 15:32:21 [debug] 6500#0: *9 http header: "Accept-Language: pt-pt"
2015/07/06 15:32:21 [debug] 6500#0: *9 http header: "Cookie: cookie=true; lang=pt; _ga=GA1.2.894621310.1424776292"
2015/07/06 15:32:21 [debug] 6500#0: *9 http header: "Connection: keep-alive"
2015/07/06 15:32:21 [debug] 6500#0: *9 http header: "DNT: 1"
2015/07/06 15:32:21 [debug] 6500#0: *9 http header: "User-Agent: Mozilla/5.0 (iPhone; CPU iPhone OS 7_1_2 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) Version/7.0 Mobile/11D257 Safari/9537.53"
2015/07/06 15:32:21 [debug] 6500#0: *9 http header done
2015/07/06 15:32:21 [debug] 6500#0: *9 event timer del: 20: 1436196801837
2015/07/06 15:32:21 [debug] 6500#0: *9 generic phase: 0
2015/07/06 15:32:21 [debug] 6500#0: *9 rewrite phase: 1
2015/07/06 15:32:21 [debug] 6500#0: *9 http script var
2015/07/06 15:32:21 [debug] 6500#0: *9 http script var: "Mozilla/5.0 (iPhone; CPU iPhone OS 7_1_2 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) Version/7.0 Mobile/11D257 Safari/9537.53"
2015/07/06 15:32:21 [debug] 6500#0: *9 http script regex: "(iPhone|iPod|iPad|Android|BlackBerry|webOS|Windows Phone)"
2015/07/06 15:32:21 [notice] 6500#0: *9 "(iPhone|iPod|iPad|Android|BlackBerry|webOS|Windows Phone)" matches "Mozilla/5.0 (iPhone; CPU iPhone OS 7_1_2 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) Version/7.0 Mobile/11D257 Safari/9537.53", client: 193.137.170.139, server: www.domain.com, request: "GET / HTTP/1.1", host: "www.domain.com"
2015/07/06 15:32:21 [debug] 6500#0: *9 http script if
2015/07/06 15:32:21 [debug] 6500#0: *9 http script regex: "^/$"
2015/07/06 15:32:21 [notice] 6500#0: *9 "^/$" matches "/", client: 193.137.170.139, server: www.domain.com, request: "GET / HTTP/1.1", host: "www.domain.com"
2015/07/06 15:32:21 [debug] 6500#0: *9 http script copy: "http://m.domain.com/"
2015/07/06 15:32:21 [debug] 6500#0: *9 http script capture: ""
2015/07/06 15:32:21 [debug] 6500#0: *9 http script regex end
2015/07/06 15:32:21 [notice] 6500#0: *9 rewritten redirect: "http://m.domain.com/", client: 193.137.170.139, server: www.domain.com, request: "GET / HTTP/1.1", host: "www.domain.com"
2015/07/06 15:32:21 [debug] 6500#0: *9 http finalize request: 301, "/?" a:1, c:1
2015/07/06 15:32:21 [debug] 6500#0: *9 http special response: 301, "/?"
2015/07/06 15:32:21 [debug] 6500#0: *9 http set discard body
2015/07/06 15:32:21 [debug] 6500#0: *9 xslt filter header
2015/07/06 15:32:21 [debug] 6500#0: *9 HTTP/1.1 301 Moved Permanently
