sub joiny {
  my ($ref, $thing) = @_;
  $$ref = join q[,], $$ref, $thing;
}

sub process (&$;$) {
  my ($code, $cmd, $skipfields) = @_;
  my @lines = `$cmd`;
  for (@lines) {
    chomp;
    my @array = split /,/;
    if ($skipfields) {
      shift @array for 1..$skipfields;
    }
    local $_ = \@array;
    $code->();
  }
}

process {
   for my $i (0 .. $#$_) {
      joiny \($disks_by_date{$date}[$i]), $_->[$i];
   }
}
q{grep DISKBUSY $nmondir/$files_by_date{$date} | grep -v Busy}, 2;

process {
   for my $i (0 .. 1) {
      my $used = 100 - $_->[2 + $i];
      joiny \($mem_by_date{$date}[$i]), $used;
   }
}
q{grep ^MEM, $nmondir/$files_by_date{$date} | grep -v Memory};