I'd say this is a matter of trust. If manager^3 trusts other peoples' opinions more than of his own perl guru, well, anything you dig up is doomed not to be weighed anyway. Also, seeking an article that specifically debunks an arbirtatry remark about anything (in your case, about Perl's insecurity), I think, is not really a sufficient strategy by itself, because "fools ask questions that wise men cannot answer".

Following this, if I'd be confronted with "Perl is insecure" I'd answer "this is not true" without further explanations; if the other side would be then interested in a dialog, then definitely articles, examples, and documentations can be discussed. Or, simply put, now you are prepared to discuss articles with a reasonable person, and I'm saying that it might not necessarily be so.