| Expr_not of whenexpr (** boolean not *)
| Expr_add of whenexpr * whenexpr (** arithmetic addition or string cat *)
| Expr_sub of whenexpr * whenexpr (** arithmetic subtraction *)
| Expr_not of whenexpr (** boolean not *)
| Expr_add of whenexpr * whenexpr (** arithmetic addition or string cat *)
| Expr_sub of whenexpr * whenexpr (** arithmetic subtraction *)