use strict;
use warnings;
use Benchmark qw(cmpthese);
use List::MoreUtils;

my @data;                                   # AB
for ( 1 .. 1e4 ) {
    push @data, int( rand 1e6 );
}

my @lines;                                  # BU
for ( 1 .. 1e3 ) {
    my $line = int( rand 1e6 );
    $line .= chr(9) . int( rand 1e6 ) while length( $line ) < 4096;
    push @lines, $line;
}

my @values = map {int rand 10} 1 .. 1000;   # GF

my $data;
$data = \@data;
#$data = \@lines;
#$data = \@values;

sub uniq1 {  # copied from List::MoreUtils
    my %h;
    map { $h{$_}++ == 0 ? $_ : () } @_;
}

sub uniq2 {
    my %h;
    grep { $h{$_}++ == 0 } @_;
}

sub uniq3 {  # OP
    my %h;
    grep {$h{$_} = undef} @_;
    keys %h;
}

sub uniq4 {  # BrowserUk
    my %h;
    undef @h{ @_ };
    keys %h;
}

cmpthese(-1, {
    'uniqM'  => sub { my @uniq = List::MoreUtils::uniq(@$data) },
    'uniq1'  => sub { my @uniq = uniq1(@$data) },
    'uniq2'  => sub { my @uniq = uniq2(@$data) },
    'uniq3'  => sub { my @uniq = uniq3(@$data) },
    'uniq4'  => sub { my @uniq = uniq4(@$data) },
});