use 5.012;
use strict;
use warnings;
use Data::Dump qw/pp dd/;

use Benchmark qw( cmpthese ) ;
use Test::More;

use B::Deparse;
my $deparse = B::Deparse->new();
use constant SHOW_DEPARSE => 1;


my (@keys, @values, %h, $expected);

BEGIN {
    my $n_keys = 6;
    my ( $first_key, $first_value ) = ("xxxxa",12345);
    push @keys,   $first_key++ for 1.. $n_keys;
    push @values, $first_value++ for 1.. $n_keys;
    @h{@keys} = @values;                #  init hash
    $expected = join ",", @values;
    eval <<"__CODE__";
      sub slice_explicit {
          join ",", \@h{ qw/@keys/}
      }
__CODE__
}

warn "hash %h: ", pp(\%h) ,"\n";




use constant LIST=>(@keys);

my @list= @keys;

my $h_subs =
          {
           map_var        => sub{ join ",", map { $h{$_} } @list },
           map_const      => sub{ join ",", map { $h{$_} } LIST  },
           slice_var      => sub{ join ",", @h{@list} },
           slice_const    => sub{ join ",", @h{LIST()} },
           slice_explicit => \&slice_explicit,
          }
  ;



cmpthese( -5, $h_subs );

# --- test validity
while ( my ($name,$sub) = each %$h_subs ) {
    my $result = $sub->();
    is($result, $expected, $name);

    # --- show code
    say $deparse->coderef2text($sub)
      if SHOW_DEPARSE and $name ~~ [qw/slice_const slice_explicit/];
}
done_testing();