Deep nesting segfault

# I've found this problem initially by using Coro with XML::LibXML;
# XML::LibXML::Error object on large invalid documents can contain lots of nested objects

sub more_nesting {
    return bless { x => shift } => "A"
}

sub build_deep {
    my $depth = shift;

    my $x;
    $x = more_nesting($x) for 1..shift();
    undef $x; # segfault happens at this point
}

# number varies on various systems and perl versions;
# perl5.8 breaks somewhere between 20k and 30k, perl5.10 even before 20k
build_deep(30_000);

use Coro;
async(sub {
    build_deep(300) # critical number for my perl/system is 291
})->join;