In general, use a hash, with your values as the keys, to find unique items.

@array = qw(1 2 3 4 5 5);
$hash  = { map { $_ => 1 } @array };
my @sorted_unique_values = sort keys %$hash;
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Perlfaq lists a more efficient way of doing this for a pre-sorted array

ViceRaid

updated: added a link to FAQ, since it's FA.