use strict;
use warnings;
my ($outer_hash, $new_hash);

$outer_hash->{backupsize} = [{
                              'totalsize' => '89',
                              'hostname' => 'aaaa',
                              'application' => 'IDB'
                            },
                            {
                              'application' => 'IDB',
                              'hostname' => 'aaaa',
                              'totalsize' => '32770'
                            },
                            {
                              'application' => 'SAP',
                              'hostname' => 'bbbb',
                              'totalsize' => '14'
                            }];
for my $entry(@{ $outer_hash->{backupsize} }){
    next unless $entry->{hostname} and $entry->{application} and $entry->{totalsize};
	$new_hash->{$entry->{hostname}} {$entry->{application}} += $entry->{totalsize};
}

for my $h (sort keys %$new_hash){
	print "HOST:$h:\n";
	for my $app(keys %{ $new_hash->{$h}}){
		print "\t",$new_hash->{$h}{$app},"\t$app\n";
	}
}