do {
    my $outer;

    do {
        my $inner1; # $inner1 memory is allocated
    }; # $inner1 memory is released
    
    do {
        my $inner2;  # $inner2 memory is allocated

        $outer = \$inner2; # $outer now references $inner2's memory
    }; # $inner2 goes out of scope but isn't released - referenced by $outer
}; # $outer goes out of scope and is released which also releases memory for $inner2