Rewriting Specific to more General - apache

Question

I'd like to do a mod_rewrite so that:
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
Any requests to users/ goes to index.php?login=(whatever).
RewriteRule ^users/(.+) ?login=$1 [NE,L]
Any other requests, outside of users/, goes to the same place.
RewriteRule ^(.+) users/?login=$1 [NE,L]
but the second part is producing a 500 Internal Server Error
I was asked to explain it, so here are some examples:
if "domain.com/aaa/" exists, it goes to "domain.com/aaa/"
if "domain.com/bbb/" does not exist, it goes to "domain.com/users/?login=bbb"
if "domain.com/ccc.html exists, it goes to "domain.com/ccc.html"
if "domain.com/ddd.html does not exist, it goes to "domain.com/users/?login=ddd.html"
meanwhile, "domain.com/users/eee" goes to "domain.com/users/?login=eee" since that's the primary condition, and the second condition is a fallback or more general catchall.

Answer 1

This should work. You have to repeat the conditions, they don't carry over to the next rule.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^users/(.+)$ /users/?login=$1 [NE,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.+)$ /users/?login=$1 [NE,L]
Assuming that the /users/ directory does actually exist.
Or this is more efficient, if you're not running any rules later. It prevents any processing of existing items and avoids doubling up the file-system checks.
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^users/(.+)$ /users/?login=$1 [NE,L]
RewriteRule ^(.+)$ /users/?login=$1 [NE,L]