my @cards = (
    {
        name => "Fireball",
        cost => { fire=>2, air=>1 },
        # other card information...
    },
    {
        name=>"Ice wall",
        cost=>{ water=>3, frost=>5 },
    },
    {
        name=>"Lightning bolt",
        cost=>{ air=>2, electricity=>4 },
    },
);