use Benchmark 'cmpthese';
use strict;

my @x = map join(',', split(//, rand(10000))), 0..80000;
my %y;

cmpthese(-2,
         {'@y{@x}'   => sub { undef %y; @y{@x} = undef },
          '%y = map' => sub { undef %y; %y = map(($_ => undef), @x) }
         }
        );

print 0+%y,$/;

##</code><code>##

         s/iter %y = map   @y{@x}
%y = map   2.45       --     -49%
@y{@x}     1.25      97%       --

##</code><code>##

# ...snip
  my ($n,$i,@n,@temp,%arrangements);
  # get size and create all permutations (comma separated)
  $n = 8;        @n = (1..$n);
  $i = 0;        $temp[&_fact($n)-1] = 1; # _fact := n!

  $|++;
  permute { $temp[$i++] = join(',',@n) } @n;
  print STDERR scalar(localtime),$/;
  @arrangements{@temp} = undef;
  print STDERR scalar(localtime),$/;

##</code><code>##

computing 8-arrangements...
Mon Sep 30 15:30:31 2002
Mon Sep 30 15:33:35 2002