#!/usr/bin/perl
use strict;
use warnings;
use diagnostics;
use Data::Dumper;
my @array = ( 1, 2, 3, 4, 5, 1, 2, 3, 99 );
my %seen = ();
my @unique_elements = ();
foreach my $element (@array)
{
    push (@unique_elements, $element) unless
        $seen{$element}++;
}

print Dumper @array;
print Dumper @unique_elements;