my %hash   = map { $_, 1 } @array;

 # or a hash slice: @hash{ @array } = ();
 # or a foreach: $hash{$_} = 1 foreach ( @array );
  
 my @unique = keys %hash;
  
 my @unique = ();
 my %seen   = ();
  
 foreach my $elem ( @array )
   {
     next if $seen{ $elem }++;
     push @unique, $elem;
   }