`((unless (typep ,(or prefix per-line-prefix) 'string)
(error 'type-error
:datum ,(or prefix per-line-prefix)
:expected-type 'string))))
,@(when (and suffixp
`((unless (typep ,(or prefix per-line-prefix) 'string)
(error 'type-error
:datum ,(or prefix per-line-prefix)
:expected-type 'string))))
,@(when (and suffixp