What compiler directives exists?

Great question. Something I'd like to know. Good thing I searched before posting a topic :) I was gonna post this example:

Global Debug=0

?Mac
Print "On mac"
?

?win32
Print "On"
Print "Windows"
?

?linux
Print "On linux"
?

?debug
Print "In debug mode"
Global Debug=1
?

If Debug=0 Then Print "In release mode"

I've sortof made my own Release mode handler above, I'd like to know what the "?" thing for it is though. Since, Release is also a keyword so you cant use it. This stuff really should be documented