sub read_chunk {
  my ($fh,$mod) = @_;
   
  my $chunk;
  while ( <$fh> ) {
    $chunk .= $_;
    return $chunk unless $. % $mod;
  }
  return $chunk;
}
 
open my $fh, "<", \$string;
while ( my $chunk = read_chunk( $fh, 14 ) ) {
  print $chunk;
  print "-"x5,"\n";
}