please try to condense code to the relevant parts or mark them better.

I really started counting the lines till 35 before I saw your comment.

something like:

 $line = <FILE>;                 #  <---------- 35
    # this line doesn't work. don't know what's wrong here..
[download]

is easier to find.

anyway, you did it twice:

  @buf = <FILE>;                     # you reading all lines of FILE i
+nto @buf
  foreach $line (@buf) {             # OK! (well, "my $line" would be 
+better)
     $line = <FILE>;                 # but now reading again a single 
+line !?! 
                                     #     which is  undef after EOF
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please less cargo cult programming!

Don't c&p different approaches from other snippets, better try to understand what's happening.