use Statistics::Descriptive;
    
    my @ranges = (19, 29, 39); # 1..19, 20..29, 30..39
    
    my $stat = Statistics::Descriptive::Full->new;
    $stat->add_data( 12, 14, 15, 20, 21 );
    
    my %dist = $stat->frequency_distribution(\@ranges);
    printf " %5d: %4d\n", $_, $dist{$_} for @ranges;