Under POSIX, the behavior of a program after an involuntary SIGSEGV is undefined. That means that you maybe can kill 11, $pid and catch it in the $pid process, but a genuine segfault may never return from whatever libc call generated it.

Setting signal handlers and capturing output are quite orthogonal. If you can do each, you can do both. I recommend piped ("magic") open for capturing output with a little more control than is given by backticks.

my $fh;
my $cpid = do {
    local $SIG{SEGV} = \&myhandler;
    open $fh, '-|', '/path/to/prog', @args or die $!;
};
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