The second paper mentions BLACKER and MLS, but nothing about perl. The closest perl comes to MLS is "taint" mode, but that seems a stretch. The first paper is pay-walled. Are you sure you're not thinking of SELinux?
I wanted to link it but nothing came up in my bookmark search. As is typical. I think my bookmarks are too packed for search to even work right. So, I just described what I read in the past.
http://cahighways.org/wordpress/?p=5460