use strict;

package Grandpa;
sub hello {
  my $class = ref $_[0] || $_[0];
  print "How do you do, from $class.\n";
}

package Dad;
our @ISA = 'Grandpa';
sub hello {
  my $class = ref $_[0] || $_[0];
  print "Hiya from $class!\n";
}

package Me;
our @ISA = 'Dad';

package main;

my $me = bless {}, 'Me';         # look Ma, no constructor!
$me->hello;

__END__

% perl say_hello.pl
Hiya from Me!