> IIRC in .htaccess omit the leading /
What that means ? IIRC ????


> You need a condition to test each part of the querystring
> RewriteCond %{QUERY_STRING} lang=1
> RewriteCond %{QUERY_STRING} var1=([^&]+)
> RewriteRule ^index\.php$ /fr/%1 [L,PT]
>
> RewriteCond %{QUERY_STRING} lang=1
> RewriteRule ^index\.php$ /fr [L,PT]
>
> RewriteCond %{QUERY_STRING} lang=0
> RewriteCond %{QUERY_STRING} var1=([^&]+)
> RewriteRule ^index\.php$ /en/%1 [L,PT]
>
> RewriteCond %{QUERY_STRING} lang=0
> RewriteRule ^index\.php$ /en [L,PT]
>
> If the list of language numbers grows large, consider
> a rewritemap -in server config rather than .htaccess-
>
> Some pitfalls ahead, not quite sure what you are after too
>
> HansH

I try what you have said but it doesn't work.
Do you have any web adress to have more details about RewriteRule ?