Underscore in GET-query and $args

[EveryonE]

If HTTP GET in query string contains underscore (_) as %5F:
f.e. GET /index.php?user%5Fid=50
then I can't check this with
if ($arg_user_id ~* ^50$)
or
if ($arg_user%5Fid ~* ^50$).

For GET /index.php?user_id=5 all fine.

Posted at Nginx Forum: http://forum.nginx.org/read.php?21,16373,16373#msg-16373