Canonicalisation prevention via .htaccess file.

Hello,

I've got the htaccess to direct mysite.com to go to www.mysite.com and www.mysite.com/index.php to www.mysite.com however I'm still able to call duplicates pages from my site like below;

http://www.mysite.com/page1.htm can be opened (this is OK) - however I can access it also via this URL http://www.mysite.com/page1.htm/

Any ideas how can I prevent a slash at the end from resolving to the same page?

my htaccess contains

RewriteEngine on
RewriteCond %{HTTP_HOST} ^mysite\.com
RewriteRule ^(.*)$ http://www.mysite.com/$1 [R=permanent,L]

# The Friendly URLs part
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /.*index\.php\ HTTP/
RewriteRule ^(.*)index\.php$ http://www.mysite.com/$1 [R=301,L]

Thanks for any guidance