I believe it'll be interesting to see how things shake out when we start seeing languages implemented in Rust. We already have a wide variety of languages for the JVM, which I believe most everyone would agree is a safer environment for a language than C, and I'd bet the theory above holds up. I don't know enough to know how to test that theory, however.

Basically, I think the "newer languages" comment refers to the implementation language (C being the most common today, but probably not for more than a few more years) rather than the language itself (Perl in this case). Though I think you're entirely right that surface area plays a big role. I would be willing to bet that Perl 6 will be more secure (by some definition of "more" and "secure") than Perl 5, because the surface area of Perl 6 that is in C is much smaller (the VM, with most of the language itself being written in a subset of Perl called NQP, or Not Quite Perl).