Further to the comments from hippo and afoken, I'm a little puzzled by your input (when downloaded) and your expected output as the alignment seems inconsistent. Have you perhaps pasted some TAB characters in there?

Regarding your code:-

• Use of lexical rather than package file handles is now recommended and I would suggest that the error messages on open failure be differentiated with the file name so that you know immediately which failed rather than having to do some detective work.

• Your

  while (<FILE>) {
      $line = $_;
  [download]

  could more simply be written

  while ( my $line = <FILE> ) {
  [download]

• You pad the line to a length of 280 characters but you have forgotten to chomp the line terminator off before padding so you have a line terminator left in the middle.

• A simpler way to pad lines with spaces is to use pack with the A template, for example:-

  johngg@shiraz:~/perl/Monks > perl -Mstrict -Mwarnings -E '
  my $text = q{abcd};
  say qq{>$text<};
  $text = pack q{A10}, $text;
  say qq{>$text<};'
  >abcd<
  >abcd      <
  johngg@shiraz:~/perl/Monks > perl -Mstrict -Mwarnings -E '
  my $text = q{abcd};
  say qq{>$text<};
  $text = pack q{A2}, $text;
  say qq{>$text<};'
  >abcd<
  >ab<
  [download]

• Rather than unpacking into several scalars do so into an array and then apply double quotes to the relevant items using an array slice, something like this:-

  johngg@shiraz:~/perl/Monks > perl -Mstrict -Mwarnings -E '
  my @items = q{a} .. q{g};
  s{(.*)}{"$1"} for @items[ 0, 1, 3, 5, 6];
  say for @items;'
  "a"
  "b"
  c
  "d"
  e
  "f"
  "g"
  [download]

• Rather than multiple print statements, perhaps use a single say (if running perl 5.10 or later) and join all the items together with commas in one fell swoop, something like

  say join q{,}, @items;
  [download]

I hope these pointers are helpful and you are able to move towards a solution. Please ask further if difficulties persist.