I don't see a faster way for this. But if you need to count often, you could generate a second HoH for a one-time cost and have that and all other counts for no cost at all after that. 

my %counts=();
foreach $kid (%hoh) {
  foreach my $attribute (%$kid) {
    $counts{$attribute}{$kid->{attribute})++;
  }
}

...
print $counts{'age'}{12};

[download]

Sadly this "one-time" cost has to be paid whenever the data changes (unless you also adjust the counts in the second HoH whenever you change anything)

UPDATE: Fixed the bug in the first line thanks to warnings from johngg and chromatic. It was too much to hope that I could write even a 4-liner without a trivial bug.

In reply to Re: Find number of unique values in hash by jethro
in thread Find number of unique values in hash by rethaew

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