I'm writing a multi threaded perl script and storing the output in a csv file. I'm trying to insert a field called sl.no. in the csv file for each row entered but as I'm using threads, the sl. no. overlaps in most. Below is an idea of my code snippet.

for ( my $count = 1 ; $count <= 10 ; $count++ ) {
    my $t = threads->new( \&sub1, $count );
    push( @threads, $t );
}

foreach (@threads) {
    my $num = $_->join;
}

sub sub1 {
    my $num = shift;

    my $start = '...';    #distributing data based on an internal logic
    my $end   = '...';    #distributing data based on an internal logic
    my $next;

    for ( my $x = $start ; $x <= $end ; $x++ ) {
        my $count = $x + 1;

        #part of code from which I get @data which has name and age

        my $j = 0;
        if ( $x != 0 ) {
            $count = $next;
        }
        foreach (@data) {
            #j is required here for some extra code
            flock( OUTPUT, LOCK_EX );
            print OUTPUT $count . "," . $name . "," . $age . "\n";
            flock( OUTPUT, LOCK_UN );
            $j++;
            $count++;

        }
        $next = $count;
    }

    return $num;
}

I need the count to be incremented which is the serial number for the rows that would be inserted in the csv file. Any help would be appreciated.