Exclude a substring in htaccess RewriteRule redirect - .htaccess

Question

I manage an old site with multiple domain with the same name,
google has indexed some old url with the language structure
http://www.example.com/eng/whatever
and
http://www.example.it/eng/whatever
and now I don't use this structure anymore, but I want to do a redirect to my new structure
http://www.example.it/en/whatever
so everything after the /eng/ must be appended to the new structure, excluded the /eng/ substring.
But it doesn't work, I have a redirect to
http://www.example.it/en/eng/whatever
which is wrong! I did not want /eng in the redirect url
In my .htaccess I have this
#this will redirect the url with /eng/whatever to www.example.it/en/whatever, regardless from the top level domain
RewriteRule ^eng\/(.*)$ http://www.example.it/en/$1 [R=301,L]
#redirect example.com on www.example.it/en/
RewriteCond %{HTTP_HOST} ^([^.:]+\.)*example\.(com|pt)?(:[0-9]*)?$ [NC]
RewriteRule ^(.*)$ http://www.example.it/en/$1 [R=301,L]

Answer 1

Try replacing all of that with just this:
RewriteRule ^eng/(.*) en/$1 [R,L,NE,DPI]
If it works, you can change the R to R=301
Warning
To test this, you must use a new browser. This is because browsers cache 301 redirects, so your current browser will keep redirecting to the old (wrong page) without even talking to your server and hitting the new .htaccess—unless you clear the browser cache.