Would be very useful to allow optional parameters for macroses (mod_macro) and add something like <IfParameterDefined paramName> directive to use inside macro definition.
Also to allow default values to be assigned to parameters, though I suppose that could effectively be done with a `<IfParameterDefined paramName>` directive.
What about a simple syntax like this: <Macro Mymacro $p1 @p2 $p3="default value" @p4="" $p5="another default value"> Simple to write, simple to read, reasonably compact. If everybody agrees I'm ready to help adapting the code and testing.