After parsing the XML into something sane (see my previous comment), the next step is to build the hash you want:

my %applications;     

for my $item (@items) {
    if ($item->{sys_class_name} eq 'cmdb_ci_appl')  
      { $applications{$item->{u_ci_id}}{name} = $item->{name} }
    else # assume device
      { push @{$applications{$item->{u_application_id}}->{member}},
            $item->{ip_address} if $item->{ip_address} }
}
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This code has minimal consistency checks. Making it fully robust is left as an exercise for the reader.