How to redirect website home page in BVN404handler

I would like to redirect the website launch(home) page to add '/en/' at the end of the launch URL for multi language. 

I tried in BVN404handler by adding source URL as just '/' and target url as just '/en/' but this is causing issues for other redirects that already exists. it's causing recursive redirects by keep adding /en/en/en/.. for every other redirects that exists. 

Could some one please sugegst the best way to implement this ?

Regards,

Suresh