New reply for new question... Just list the important domains in @domainlist:

@domainlist = qw(hostname.foo.com host1-name.foo.com);
@DISKD = <inputfile>;
foreach $domain (@domainlist) {
  @value = grep { /\b\Q$domain\E\b/ } @DISKD;
  for $value (@value) {
     @data = split /\s+/, $value;
     $sum += $data[$#data];
  }
}
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