http://frepan.64p.org/~flora/Devel-bt-0.01/lib/Devel/bt.pm $ perl -d:bt -MB -e'(bless \(my $o = 0), q{B::SV})->REFCNT' #0 0x00007f9c3215ab0e in __libc_waitpid (pid=<value optimized out>, stat_loc=0x7fff4c5ffbe8, options=<value optimized out>) at ../sysdeps/unix/sysv/linux/waitpid.c:32 #1 0x00007f9c319168c1 in backtrace () at bt.xs:129 #2 0x00007f9c319168ec in sighandler (sig=11) at bt.xs:135 #3 <s