my $i = 30000;
my %h = (new => {});
my $r = \%h;
for (0..$i) {
   print $_, " ";
   $r = $r->{new};
   $r->{new} = {};
}
print "end\n";

##</code><code>##

...29998 29999 30000 end
Segmentation fault (core dumped)

##</code><code>##

my $i = 30000;
my %h = (new => {});
my $r = \%h;
for (0..$i) {
   print $_, " ";
   $r = $r->{new};
   $r->{new} = {};
}
undef %h;
print "end\n";