Hmm. Dividing by 256 isn't quite right, because you could get a fractional number. Maybe this is closer:

my $errcode = $? >> 8;
my $core_was_dumped = !!($? & 128);
my $signal_that_killed_it = $? & 127;
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This is from memory, so if I messed up, I'm sure someone will correct me. {grin}

-- Randal L. Schwartz, Perl hacker