my $atleastone = 1;
  while ($atleastone) {
    $atleastone = 0 ;

    my @l = () ;
    foreach my $op (@handles) {
      my $c2 ;
      ++$atleastone and (undef, $c2) = split if defined($_ = <$op>) ;   
      push @l, $c2 || "0" ;
    } ;
    print OUTFILE join("\t", @l), "\n" ;
  } ;