@a=(1, 2, 3, 3, 2, 1, 2, 2);
my @c = ();
my $last = 0;
for my $i(@a) {
    $c[$i+1] = 0 if $i < $last;
    $c[$i]++;
    $last = $i;
    push @out, join '.', grep{$_} @c;
}
print "$_\n" for @out;
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