my $digits = 2;
my @mods;
for ([0,0],[2,2],[3,6],[5,8],[6,3],[8,5]) {
    $mods[$_->[0]] = $_->[1];
}

my $min_factor = 1 . (0 x ($digits-1));

for my $a ($min_factor .. (9 x $digits)) {
    if (defined $mods[$a % 9]) {
        for (my $b = $min_factor - 1 + ($mods[$a % 9]||9); $b <= $a; $b += 9) {
            my $prod = $a * $b;
            my $fdigits = join '', sort map {split //} $a, $b;
            my $pdigits = join '', sort split //, $prod;
            if ($pdigits eq $fdigits) {
                print "$a * $b = $prod\n";
            }
        }
    }
}