You normally get this sort of error if you're printing a stack backtrack including function args, and one one of the args has been freed and since re-allocated (this can happen because the perl stack isn't reference counted, which is a long-standing bug).

So something like the following (which doesn't reproduce the error in this case, but gives you an idea of what can happen):

use Carp;
@a = (1,2);
foo(@a);
sub foo {
    @a = ();
    Carp::cluck();
}
[download]

Dave.