I get a segmentation fault (Mac OS X 10.3.4, Perl 5.8.1). I would conclude that my version of Perl is more broken than yours since dieing strikes me as less broken than segfaulting. What message do you get?
For me /(?{\/\/}/ dies with the message:
panic: unknown regstclass 0 at (name) line (line)
The SIG handler should then deform that slightly to give "perl\n" as the output to STDERR.
It would appear it works for no-one but me, oh well.