Minimal configuration

[B.R.]

Thanks for your input Francis.
What I suspected seemed old but I really don't understand the problem I am
facing.

Consider the following server configuration for some phpBB forum:
server {
        listen          80;
        server_name     b.cd;
        try_files       $uri $uri/;

        root    /var/www/phpBB3;
        index   index.html index.htm index.php;
        include fastcgi.conf;

        location /favicon.ico {
            access_log off;
            log_not_found off;
            expires 7d;
            return 204;
        }

        location ~ \.php$ {
                try_files $uri =404;
                fastcgi_pass    unix:/var/run/php5-fpm.sock;
        }
}


Requesting b.cd in the browser ends up wth a HTTP 500 error:
'[error] 12345#0: *42 rewrite or internal redirection cycle while
internally redirecting to "/", client: 12.34.56.78, server: b.cd, request:
"GET / HTTP/1.1", host: "b.cd"'

Adding / at the end of try_files so it reads:
try_files       $uri $uri/ /;
solves the problem...

Really, I don't get it.
Any insight on what is going on?
---
*B. R.*
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