my %subcat = (Foo => 3, Bar => 2, Baz => 10, Quux => 1);
my @Keys = keys %subcat;
while (my $Temp = [splice @Keys, 0, 3]){
  print "<tr>\n";
  print defined @$Temp[0] ? "  <td>@$Temp[0] ($subcat{@$Temp[0]})</td>\n"
                          : "  <td></td>\n";
  print defined @$Temp[1] ? "  <td>@$Temp[1] ($subcat{@$Temp[1]})</td>\n"
                          : "  <td></td>\n";
  print defined @$Temp[2] ? "  <td>@$Temp[2] ($subcat{@$Temp[2]})</td>\n"
                          : "  <td></td>\n";
  print "</tr>\n";
  last unless @Keys;
}