use strict;

my @rowTypes = (1, 2, 3, 3, 3, 1, 2, 3, 3, 1, 2, 1, 3);
my $count;

for my $rowType (@rowTypes) {
    if ($rowType == 1) {
        # New group
        next unless defined $count; # No processing for first or empty group
        print "$count ";
        $count = 0; # Reset count. Set to undef to skip empty group
        next;
    }
    
    ++$count if $rowType == 3;
}

print "$count " if defined $count; # Need to process the last group