Not compiling with perspective

[letypequividelespoubelles]

This constraint

(defconstraint exception_pot_pourri (:perspective stack)
  (begin
                    (is-binary  IOPCX   )
                    (is-binary  SUX     )
                    (is-binary  SOX     )
                    (is-binary  OOGX    )
                    (is-binary  MXPX    )
                    (is-binary  RDCX    )
                    (is-binary  JUMPX   )
                    (is-binary  STATICX )
                    (is-binary  SSTOREX )
                    (is-binary  INVPREX )
                    (is-binary  MAXCSX  )
                    ;;
                    (if-zero    MXP_FLAG    (vanishes! MXPX))
                    (if-not-zero    (-  INSTRUCTION RETURNDATACOPY) (vanishes! RDCX))
                    (if-not-zero    (-  INSTRUCTION SSTORE)         (vanishes! SSTOREX))
                    (if-zero    JUMP_FLAG   (vanishes!   JUMPX))
                    (if-zero    STATIC_FLAG (vanishes!   STATICX))
                    (if-not-zero    (+  INVPREX MAXCSX)
                        (begin
                            (eq!  CODE_DEPLOYMENT_STATUS  1)
                            (eq!  INSTRUCTION     RETURN)))))

returns this error :

[ERROR] constraint hub_v2.exception_pot_pourri should be of type Loobean, found Boolean

but compile if one removes the (:perspective stack)