when I run it I don't get back any links.

But you get back some errors and warnings; you should fix your code.

Did I forget to copy a line of code or something?

  my $p = HTML::LinkExtor->new(\&callback);
[download]

is passing a CODE reference of a non-existing subroutine into the method new of HTML::LinkExtor.

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}