use Data::Dumper;
my $prev_data;
while (my $data = $sth->fetchrow_arrayref()) {
  if( $prev_data
    && $data->[0] == $prev_data->[0]
    && $data->[1] == $prev_data->[1]
    && $data->[2] == $prev_data->[2]
  ){
    print $data->[4];
  }else{
    print Dumper $data;
  }
  $prev_data = $data;
}