Values beginning with the array @ and hash % sigils are passed by reference, i.e. under the default bindings:

    @array->join(', ')
    @{ ... }->length()
    %hash->keys()
    %$hash->values()

are equivalent to:

    ARRAY::join(\@array, ', ')
    ARRAY::length(\@{ ... })
    HASH::keys(\%hash)
    HASH::values(\%$hash)