Note that the OpenSSL CA.pl utility creates certificates that have a human readable textual representation in front of the PEM representation. You can use the following to skip to the certificate if you know it is a PEM certificate:

skip_to_pem_cert(In) :-
      repeat,
      (   peek_char(In, '-')
      ->  !
      ;   skip(In, 0'\n),
          at_end_of_stream(In), !
      ).