.htaccess RewriteRule with multiple GET variables?

I saw a lot of similar questions, but I couldn't solve this problem with their answers..

I'm trying to do a URL Rewrite by converting

http://example.com/myfile.php?var1=42&var2=aString

to

http://example.com/mydir/42/aString

I tried the following RewriteRule 's (one by one) :

• RewriteRule ^mydir/([0-9]+)/(.*)/(.*)$ myfile.php?var1=$1&var2=$2 [NC,L]
• RewriteRule ^mydir/([0-9]+)/(.+)/(.+)$ myfile.php?var1=$1&var2=$2 [NC,L]
• RewriteRule ^mydir/([0-9]+)/?$/?$ myfile.php?var1=$1&var2=$2 [NC,L]

I couldn't get them work.. What am I doing wrong? and how can I make it work?

Thanks !