exception for NGINX limit_req_zone

[fhal]

I got a problem with NGINX limit_req_zone. Anyone can help? The problem is that, I want to limit user access to some specific URL, for example:

/forum.php?mod=forumdisplay?
/forum.php?mod=viewthread&***

But, I do want to add an exception for below URL,

/forum.php?mod=image&*

Below is the location section of my configuration, the problem is that, for URL started with /forum.php?mod=image&*, the limitation is still applied.
Any body can help?

location ~*^/forum.php?mod=image$ {
    root           /web/www;
    fastcgi_pass   unix:/tmp/nginx.socket;
    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
    include        fastcgi_params;
    }
location ~*^/(home|forum|portal).php$ {
    root           /web/www;
    limit_conn   addr  5;
    limit_req zone=refresh burst=5 nodelay;
    fastcgi_pass   unix:/tmp/nginx.socket;
    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
    include        fastcgi_params;
    }
location ~ \.php$ {
    root           /web/www;
    fastcgi_pass   unix:/tmp/nginx.socket;
    fastcgi_index  index.php;
    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
    include        fastcgi_params;
    }

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