Even bad directions can be life critical (somebody u-turned into oncoming traffic when his GPS route-finding software told him to), so "life critical" can involve almost any kind of software. Presuming you're limiting it to software where failure is likely to be immediately lethal, with no user recourse, I'd (gag, choke) probably use Ada.

The problem is less the language than the programming discipline applied to the product. I remember reading that NASA estimated changing one line of code in Apollo mission software cost about 4 000 USD. In 1965. So, the costs associated with this level of discipline are most assuredly not trivial, and are likely to be comparable regardless of language.

Perl is not going to be running on embedded systems (for a few years), so the life critical projects are unlikely to involve something like your car's anti-lock brakes. It may involve emergency call systems (911 systems in the US) or air traffic control or, God help us, national command and control systems. In any case, the last three are likely to be very large, very complex projects, regardless of language.

One famous case -- a medical risk of computers -- involved a badly designed interface, but not any kind of "real-time" programming.