To get the total sums of cost, damage, armor, you can use the map function to accumulate the various items.

#!/usr/bin/perl
use strict;
use warnings;
use List::Util 'sum';

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 $cost = sum(map $_->{cost}, values %$weapons_ref);
my $damage = sum(map $_->{damage}, values %$weapons_ref);

print "cost: $cost  damage: $damage\n";
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Prints:

cost: 157  damage: 30
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