use strict;
use warnings;

{
    package Level1;
    sub new { bless {}, shift };
    sub display { print "Base\n" }
}

{
    package Level2;
    use base qw(Level1);
    sub display {
        my($class) = @_;
        $class->SUPER::display();
    }
}

{
    package Level3;
    use base qw(Level2);
    sub display {
                my($class) = @_;
                $class->SUPER::display();

    }
}

{
    package Level4;
    use base qw(Level3);
    sub display {
                my($class) = @_;
                $class->SUPER::display();

     }
}

my $obj = Level4->new();
$obj->display();