more simple - well.... yes and no...

#!/usr/bin/perl

my @a = ('a', 'b', 'c', 'c' ,'f', 'a', 'd');

my @b = grep (!$_{$_}++, @a);
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the 'my @b' line is the solution - it comes up with the correct info, but does involve doing a little work to get to the answer.

It's definitely more simple to write :) but as for processing times etc - I really don't know if it's going to be better or not.

It's a bit nasty to put this in your code without commenting it also, as I've got a few perl friends (none uber perl ppls, but 'know' perl), and none of them understood the intent :)