* arguments of the form 'type variable_name;' or 'x+y'.
*
* The lhs argument string will be appended to the current cmd string,
- * followed by an operator, if applicable, followd by the rhs string,
+ * followed by an operator, if applicable, followed by the rhs string,
* followed finally by a separator, if applicable. Before the
* argument is added, the @check_arg function, if present, will be
* used to check the sanity of the current arg strings.