FYI, Daniel Moller (Autonomous University of Barcelona) added a nice
option to the input script syntax, where you can now use "immediate"
equal-style variables, without naming them. E.g. this
region 1 block $((xlo+xhi)/2+sqrt(v_area)) 2 INF INF EDGE EDGE
is the same as
variable X equal (xlo+xhi)/2+sqrt(v_area)
region 1 block $X 2 INF INF EDGE EDGE
variable X delete
Released this as a 20Feb patch.