using env in proxy.conf as the realm name

Hello, I tried to define realms in proxy.conf in following way: realm $ENV{DOMAIN_NAME} { } realm $ENV{NETBIOS_NAME} { } but FreeRADIUS shows error during the start : etc/raddb/proxy.conf[7]: Parse error after "DOMAIN_NAME": unexpected token "}" Does FreeRADIUS support environmental variables ? Thanks, Andrei