add_rewrite_rule() weird behaviour

I’am actually having weird problems with add_rewrite_rule().

As soon as i use index.php? in my 2nd argument regexp, the function fails writing anything in the .htacees file.:

function qvs( $vars ){
 $vars[]= 'myvar';
}
add_action( 'query_vars, 'qvs' );
function myrewrite(){
 add_rewrite_rule('something/([0-9]+), 'index.php?pagename=something&myvar=$matches[1]' );
}
add_action( 'init', 'myrewrite', 10, 0 );

this simply doesn’t write any rule in the .htaccess file

function myrewrite(){
 add_rewrite_rule('something/([0-9]+),'something/?myvar=$matches[1]' );
}
add_action( 'init', 'myrewrite' );

A rewriteRule is written :

RewriteRule something/([0-9]+) /a-wordpress-plugins-work/something/?myvar=$matches[1] [QSA,L]

But it doesn’t work … still ending to my 404 page

add_rewrite_rule('^something/([0-9]+), '/something/?myvar=$matches[1]' );

Prints a weird rule that looks like this :
RewriteRule ^^something/([\d]+) /a-wordpress-plugins-work//something/?myvar=$matches[1] [QSA,L]

Of course none of these are working …

Really need help for this !!!

Thanks