How do I make try_files work here..

gistfile1.txt

# So, the idea here is to take USERNAME.neocities.org, and have it serve
# from /home/web/neocities/public/sites/USERNAME/REQUESTED_FILENAME

# When I try to use it, I get in error.log:
# invalid number of arguments in "try_files" directive in /etc/nginx/sites-enabled/neocities:5

server {
    root /home/web/neocities/public/sites;
    server_name neocities.org www.neocities.org ~^(?<subdomain>.+)\.neocities.org$;

    try_files $subdomain/$request_filename;

#   location / { 
#     proxy_set_header  X-Real-IP  $remote_addr;
#     proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;
#     proxy_set_header Host $http_host;
#     proxy_max_temp_file_size 0;
#
#     proxy_pass http://127.0.0.1:20000;
#     break;
#   }   
  }