[Petal] Modifiers and variables

[Jean-Michel Hiver]

>Well, now that I've figured out how TAL/TALES works, maybe it's time to
>check into METAL <g>. Does METAL use TALES in its attributes or is that
>a whole 'nother language definition?
>
With Petal it's another language definition derived from the includes 
syntax, as well as a huge big hack (... but it works!).

I don't really know how it's implemented with ZPT.