$file=IO::File->new('c:/scripts/002.txt');
  # is the same of
  $file=IO::File->new('c:/scripts/002.txt','<');

  #as

  open my $fh,       'c:/scripts/002.txt' or die "unable to open a file to read";
  # equal to
  open my $fh, '<',  'c:/scripts/002.txt' or die "unable to open a file to read";