use strict;

my $weapons_ref = {
    dagger => { cost => 8, damage => 4, armor => 0 },
    shortsword => { cost => 10, damage => 5, armor => 0 },
    warhammer => { cost => 25, damage => 6, armor => 0 },
    longsword => { cost => 40, damage => 7, armor => 0 },
    greataxe => { cost => 74, damage => 8, armor => 0 },
  };

my $sum_cost;
my $sum_damage;
my $sum_armor;

map { 
  $sum_damage += $weapons_ref->{$_}->{damage}; 
  $sum_cost += $weapons_ref->{$_}->{cost};
  $sum_armor += $weapons_ref->{$_}->{armor} 
} keys %{ $weapons_ref };

print join(' ',$sum_cost, $sum_damage, $sum_armor), '\n';

##</code><code>##

157 30 0

##</code><code>##

use strict;
use Data::Dumper;

my $weapons_ref = {
    dagger => { cost => 8, damage => 4, armor => 0 },
    shortsword => { cost => 10, damage => 5, armor => 0 },
    warhammer => { cost => 25, damage => 6, armor => 0 },
    longsword => { cost => 40, damage => 7, armor => 0 },
    greataxe => { cost => 74, damage => 8, armor => 0 },
  };

my $sum_result;
my @sum_fields = qw/cost damage armor/;

map { 
  my $name = $_;
  map { $sum_result->{$_} += $weapons_ref->{$name}->{$_} } @sum_fields
} keys %{ $weapons_ref };

print Dumper($sum_result);

##</code><code>##

$VAR1 = {
          'armor' => 0,
          'cost' => 157,
          'damage' => 30
        };