# method 1
{
  my %uniq;
  @uniq{@elements} = ();  # placing them into piles
  @uniq = keys %uniq;     # getting one from each pile
}

# method 2
{
  my %seen;
  @uniq = ();
  for (@elements) {
    push @uniq if !$seen{$_}++;  # inserting if not seen
  }
}