You have a strange definition of unique :) ... your code removes any entries which don't occur exactly once, try for example this:

my @array = qw/one one two/;

# your algorithm

print @uniques;
# prints 'two'
# and I would expect 'onetwo'
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So changing that and putting it a bit shorter:

my %count = ();
my @uniques = grep {! $count{$_}++} @array;
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... and btw this should be in the FAQs somewhere.

-- Hofmator