use strict;
use warnings;
my @result;
my $count = 0;
for (<"j*.txt">) {
  open my $fh, "<", $_ or die "Cannot open $_ $!\n";
  while(<$fh>){
    chomp;
    $result[$.-1][$count] = $_;
  }
  $count++;
}
for my $line (@result) {
  print join( ",", map { $_//"" } @$line ), "\n";
}