Changing file name in htaccess gives error 500 - apache

Question

I have set
mydomain.com/page
to point to
mydomain.com/script.cgi
using htaccess and mod_rewrite, which works perfectly. BUT, when I change the file name and the associated rewrite rule I get error 500. Initially I thought it was a browser caching issue, but clearing the cache doesn't help. Here's the htaccess file:
Options +FollowSymlinks
RewriteEngine On
RewriteBase /
RewriteCond %{HTTPS} off
RewriteRule .* https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^page(.*)?$ /script.cgi$1 [NE,NC,L]
As I said this works perfectly - until I change the file name and the rule. If I change my script file name to script2.cgi and modify the rule to point to script2.cgi, it throws an error. Is it some kind of server caching issue?

Answer 1

I found the answer. It won't be obvious here because I used placeholder names. The problem was my alias folder and destination script began with the same letters.
/page -> /page.cgi
Because I used ^page(.*)?$ in the rule, it was also matching page.cgi thus creating an infinite loop. The answer is to either change the rule to ^page$ to match the entire alias name only, or change the name of the script to something else. Thanks everyone. Hope this helps someone else.