#! /usr/bin/perl

use strict;
use warnings;

my @array = qw(user1 user2 user3 user2 user4 user1);
my @passwd = qw(pass1 pass2 pass3 pass2 pass4 pass1);
my %seen;
my @unique = grep{!$seen{$array[$_]}++}(0..scalar(@array)-1);
for(@unique){
    print $array[$_],"\t",$passwd[$_],"\n";
}