def set_variable(var, val, override=false)

      fexp, v = locate_set_var(var, override) || locate_var(var)

      fexp.un_set_variable(:set, v, val, (fexp.h.fei != h.fei)) if fexp
    end
def set_variable(var, val, override=false)

      fexp, v = locate_set_var(var, override) || locate_var(var)

      fexp.un_set_variable(:set, v, val, (fexp.h.fei != h.fei)) if fexp
    end
Sets a variable to a given value.
 (will set at the appropriate level).