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 },
    },
);

##</code><code>##

my @players = (
    {
        name=>"Joe",
        mana =>{ fire=>5, air=>5, electricity=>5 },
        # other information about player
    },
    {
        name=>"Audrey",
        mana =>{ water=>5, frost=>10 },
    },
);

##</code><code>##

sub can_cast {
    my ($rPlayer, $rCard) = @_;

    for my $manaType (keys %{$rCard->{cost}}) {
        return 0 if ! exists $rPlayer->{mana}{$manaType};
        return 0 if $rPlayer->{mana}{$manaType} < $rCard->{cost}{$manaType};
    }

    # Nothing rejected, so we can cast it!
    return 1;
}

##</code><code>##

$ cat mana.pl
use strict;
use warnings;

my @cards = (
   <<< snip >>>
);

my @players = (
   <<< snip >>>
);

# Show which players can cast which spells

for my $rPlayer (@players) {
    print "$rPlayer->{name} can cast: ";
    my $cnt=0;
    for my $rCard (@cards) {
        if (can_cast($rPlayer, $rCard)) {
            ++$cnt;
            print "$rCard->{name} ";
        }
    }
    if (!$cnt) {
        print "NOTHING!";
    }
    print "\n";
}

sub can_cast {
   <<<snip>>>
}

$ perl mana.pl
Joe can cast: Fireball Lightning bolt
Audrey can cast: Ice wall