Regarding complex hashes in perl

I have a hash of hash, where my first key is name and second is some classes like level A, level B, level C and the values is d total number of students..

%hash{name}->{class}->number

So I fill my hash and everything is done开发者_StackOverflow中文版 but now when I print I get the number but if suppose a student name is in level A and level C and not in level B it should show

Name:level A = 1
     level B = 0
     level C = 1

How can I get my result like this? Please help me out..

use strict;
use warnings;

my %scores = (
    homer => { levA => 1, levC => 2 },
    bart =>  { levA => 3, levB => 4 },
);

my %all_levels = map { map {$_ => 1} keys %$_  } values %scores;

for my $h (values %scores){
    for my $lev (keys %all_levels){
        $h->{$lev} = 0 unless exists $h->{$lev};
    }
}

This is a bit of a stretch, but what I think you're after is to assign a value of zero to all (name,class) pairs for which $hash{name}->{class} is undefined. So, given that...

my @classes; #First, we grab all of the possible classes.

foreach my $name (sort keys %hash)
{
    foreach my $class (sort keys %{$hash->{$name}})
    {
        push @classes, $class unless $class~~@classes;
    }
}

@classes=sort @classes #or sort{$a<=>$b}@classes, depending on the datatype...

foreach my $name(sort keys %hash)
{
    foreach my $class(@classes)
    {
        $hash->{$name}->{$class}=0 unless defined $hash->{$name}->{$class};
    }
}