[nginx] Configure Nginx with proxy_pass

I'm trying to configure Nginx to proxy stuff on a subdomain: dev.int.com

I want dev.int.com to be proxied to IP:8080, and dev.int.com/stash to be proxied to IP:7990

Here's my current config file

server {
listen   80;
server_name  dev.int.com;
access_log off;
location / {
    proxy_pass http://IP:8080;
    proxy_set_header    Host            $host;
    proxy_set_header    X-Real-IP       $remote_addr;
    proxy_set_header    X-Forwarded-for $remote_addr;
    port_in_redirect off;
    proxy_redirect   http://IP:8080/jira  /;
    proxy_connect_timeout 300;
    location ~ ^/stash {
        proxy_pass http://IP:7990;
        proxy_set_header    Host            $host;
        proxy_set_header    X-Real-IP       $remote_addr;
        proxy_set_header    X-Forwarded-for $remote_addr;
        port_in_redirect off;
        proxy_redirect   http://IP:7990/  /stash;
        proxy_connect_timeout 300;
    }
}

    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
    root   /usr/local/nginx/html;
    }
}

However, /stash redirects are going to /. What am I doing wrong?

Nginx prefers prefix-based location matches (not involving regular expression), that's why in your code block, /stash redirects are going to /.

The algorithm used by Nginx to select which location to use is described thoroughly here: https://www.digitalocean.com/community/tutorials/understanding-nginx-server-and-location-block-selection-algorithms#matching-location-blocks