Indeed! I just found that myself, and am looking into it. That function was only added to Net::SSLeay in January, so I'll need to upgrade. Unfortunately, the usage information for those low-level functions is quiet terse. I'm currently puzzling over this, and how to get a "value corresponding to openssl's X509 structure"

my $rv = Net::SSLeay::X509_STORE_add_cert($store, $x);
 # $store - value corresponding to openssl's X509_STORE structure
 # $x - value corresponding to openssl's X509 structure
[download]