my $person = Person.new(:life(100), :attack(1), :spell(2));
$person.weapons<a> = Weapon.new(:name<sword>, :powerLow(3), :powerHigh
+(5) );
$person.weapons<s> = Weapon.new(:name<spell>, :powerLow(0), :powerHigh
+(7) );
[download]

I suggest:

given my $person = Person.new(...) {
    given .weapons {
        .<a> = Weapon.new(...);
        .<b> = Weapon.new(...);
    }
}
[download]

Or simply:

given my $person = Person.new(...) {
    .weapons = {
        a => Weapon.new(...),
        b => Weapon.new(...)
    };
}
[download]

Or maybe just

my $person = Person.new(
    ...,
    weapons => {
        a => Weapon.new(...),
        b => Weapon.new(...)
    }
};
[download]

I personally think :pair() style should not be used for setting anything that's clearly key and value in a hash or object. :foo() is very nice for things that alter behaviour:

my $socket = Socket.new( 
    localport => 80,
    localaddr => '127.0.0.1',
    :proto<tcp> :listen(5) :timeout(500) :reuse
);

my @users = slurp '/etc/passwd' :chomp;

my @even = 2..10 :by(2);
[download]

All code is untested.