++++ for line numbers in your code, -- for the mess in the intro, makes ++ ;-)

Answer to your first question: change line 27 to

    print $dub_key,Dumper($dub_values);
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More critics:

• Line 0: I guess you forgot to use Data::Dumper;
• Line 16: better write
  or die "dublin file '$element' did not open: $!\n"
  so you see what fubar the $element is
• Line 19: better write
  $dub_values = (split /:/,<FILE>) [0]
  if you want just the first element from split; if you want an anonymous array, write
  $dub_values = [ split /:/,<FILE> ]
  
• Lines 21-23: weird usage of Data::Dumper

hth,
--shmem

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