Note : This is not really a question because I already found the answer but since I didn't find it easily here I will post it so that it can benefit others.
Question : How to read a concatenated PEM file as the one used by apache/mod_ssl directive SSLCACertificateFile ?
Answer (source) :
cat $file|awk 'split_after==1{n++;split_after=0} /-----END CERTIFICATE-----/ {split_after=1} {print > "cert" n ".pem"}'