Nginx config dynamic $host ENV variable

I am looking for a better way to set Environment Variable based on dynamic $host value in Nginx config. What regex expression could be used?

For example, $preferred_hostid has different value based on the $host. I can use hard code if statement to set their value. However, there are so many host values.

client1.shop.abc.com

client2.shop.abc.com

clientN.shop.abc.com

server{

listen 80 default_server;

set $preferred_hostid '.abc.com';
if ($host = 'client1.shop.abc.com'){
    set $preferred_hostid '.xyz.com'
}
if ($host = 'client2.shop.abc.com'){
     set $preferred_hostid '.lmn.com'
}
if ($host = 'client3.shop.abc.com'){
     set $preferred_hostid '.hij.com'
}

}

What is the better way to handle this scenario? Thanks