my $AoH_class = [ 
                  { 
                    'class' => 'Algebra',
                    'room'   => '204',
			         },
                  { 
                    'class' => 'Science',
                    'room'   => '413',
			         }			         
		          ];

my @AoH_algebra = ( 
                    {
                      'name'   => 'Fred',
                      'level'  => 'junior',
                    },
                    {
                      'name'   => 'Barney',
                      'level'  => 'senior',
                    }
                  );
$AoH_class->[1]{'students'} = \@AoH_algebra;

print Dumper($AoH_class);