I like having a config file like: host thatmachine.example.org port 9991 dbhost server.example.org ... which I can definitely parse myself. But it

I like having a config file like: host thatmachine.example.org port 9991 dbhost server.example.org ... which I can definitely parse myself. But it's also valid Tcl, if host/port/dbhost are defined proc's! So this allows people to be able to create config files like: set mydomain example.org host thatmachine.$mydomain dbhost server.$mydomain if {$mydomain == example.org} { port 12345 } else { port 9991 } I don't expect people to create huge programs in their config files, but being able to give them a "full-blown programming language" for free is sometimes desirable.