The answer yes; unless they're catching the exception first then neutralizing it (which would be dumb, but it happens). I think the key is, the ref is false. Maybe try it with eval to double check, I do see croak all over his module,

local $@;
my $book = eval { ReadData("$upload_dir/yello$filename") };
if ($@ or not $book) {
  # ... handle error
}
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You should also head off some issues by checking to see if "$upload_dir/yello$filename" even exists and is readable.