[syslog-ng] how rewrite the HOST macro?

Hello, i want to use syslog-ng to receive and log messages, the goal is to write log messages to: /appli/syslog-ng/logs/server0/messages but server0 can have multiples names: server0 server0e1 server0e2 server0g1 server0g2 server0gt1 etc... how can retrieve the name "server0" only ? Regards, Mobidyc