How can I use one .env file for multiple Document roots in Laravel

We use Laravel and have multiple subdomains/domains set up in our servers for different clients. Most of the .env parameters - API urls, DB configurations etc are the same for all clients. Some parameters such as hashing keys may be different. Is it possible to store common parameters in one 'global' .env file,'source' them from it and then add the client-specific parameters in a 'local' .env file? As of now, we have to edit the .env file for each client when we add a new parameter.

via Chebli Mohamed