.htaccess rewrite to the same url and pass get params - regex

Question

All the examples I see with RewriteRule are something like RewriteRule ^([a-z])$ index.php?example=$1
But I have the following case: I want the
example.com/en/something
to rewrite to
example.com/something?lang=en
And that applies to all things in the place of something.
Basically I want to only take the first parameter if it's en or ru and rewrite to the same link but only to pass it as a get parameter
So
example.com/en/something-else/anything
also rewrites to
example.com/something-esle/anything?lang=en
How can I do that ?
UPDATE
I tried this RewriteRule ^(en|ru)/(.*)$ $2?lang=$1 but it says that the page is not found (it returns the 404 page from my application not from the server).

Answer 1

I managed to fix it after all.
This is my .htaccess now:
# SEO URL Settings
RewriteEngine On
# If your opencart installation does not run on the main web folder make sure you folder it does run in ie. / becomes /shop/
RewriteBase /avc0135/
#Language
RewriteRule ^(en|ru|bg)/(.*)$ $2?lang=$1
RewriteRule ^(en|ru|bg)$ ?lang=$1
#Language
RewriteRule ^sitemap.xml$ index.php?route=extension/feed/google_sitemap [L]
RewriteRule ^googlebase.xml$ index.php?route=extension/feed/google_base [L]
RewriteRule ^system/storage/(.*) index.php?route=error/not_found [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !.*\.(ico|gif|jpg|jpeg|png|js|css)
RewriteRule ^([^?]*) index.php?_route_=$1 [L,QSA]
After a few searches on how exactly does .htaccess works I managed to figure out the RewriteRule, the problem after that was that the #Language block was at the bottom, I moved before everything else and it worked.