Cool. Here is a somewhat more memory-efficient alternative:

perl -ne '$a[$h{$_}]= ""; push @a, $_; $h{$_}= $#a; END{print for @a}'
+ file
[download]

Or, if you want to cut even that memory foot-print (or does it?) roughly in half (at the cost of more CPU):

perl -ne '$h{$_}= $.; END{print for sort {$h{$a} <=> $h{$b}} keys %h}'
+ test.txt
[download]

                - tye