use strict;
use warnings;

use Benchmark q{cmpthese};

my @arr = ( q{a} .. q{z} ) x 1000;

cmpthese(
   -10,
   {
       useGrep  => sub
          {
              my %seen;
              return grep { ! $seen{$_} ++ } @arr;
          },
       useSlice => sub
          {
              my %seen;
              @seen{@arr} = ();
              return keys %seen;
          },
   });