To be able to make a call at data stored in [value]s in [if] and [expr]
would be fantastic. When you want to use formulas where the members
change a lot somewhere else in the patch, it'll be handy not to have to
get them out of their v object again each time... I'd be very happy to
write [expr $i1 * ((grid_unit * factor)*zoom_x)] instead of using [t b b
b] and such...