| Expr_eq of whenexpr * whenexpr (** == *)
| Expr_ge of whenexpr * whenexpr (** >= *)
| Expr_gt of whenexpr * whenexpr (** > *)
+ | Expr_ne of whenexpr * whenexpr (** != *)
| Expr_not of whenexpr (** boolean not *)
| Expr_add of whenexpr * whenexpr (** arithmetic addition or string cat *)
| Expr_sub of whenexpr * whenexpr (** arithmetic subtraction *)