def unset_variable(var, override=false)

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

      fexp.un_set_variable(:unset, v, nil, (fexp.h.fei != h.fei)) if fexp
    end
def unset_variable(var, override=false)

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

      fexp.un_set_variable(:unset, v, nil, (fexp.h.fei != h.fei)) if fexp
    end
Unbinds a variables.