I'm trying to set up multiple subfolder to subdomain redirect like this:

location ~ ^/\~([^/]+)/(.*)$ {
  location ~ ^/\~ask/(.*)$ {
    rewrite ^(.*)$ http://forum.site.com$1 permanent;     
  }

  location ~ ^/\~forum/(.*)$ {
    rewrite ^(.*)$ http://forum.site.com$1 permanent;     
  }

  location ~ ^/\~qa/(.*)$ {
    rewrite ^(.*)$ http://forum.site.com$1 permanent;     
  }
}

The idea is that all requests to site.com/ask, site.com/forum and site.com/qa will be redirected to forum.site.com. With the above code, only redirects from site.com/ask are working. What could be wrong with the rest and is there a better way to setting them up?