How many kind numbers 9*9 multiplation table has.

99seen.pl

#!/usr/bin/perl

use strict;
use warnings;

my %seen;

for my $i (1..9) {
    for my $j (1..9) {
        $seen{$i * $j}++;
    }
}

my @seen = keys %seen;

print "9*9 tables has " . @seen . " kind numbers\n";

__END__

$ perl 99seen.pl
9*9 tables has 36 kind numbers