Comma quibbling

sub comma-quibbling(@A) {
    <{ }>.join: @A < 2 ?? @A !! "@A[0..*-2].join(', ') and @A[*-1]";
}

say comma-quibbling($_) for
    [], [<ABC>], [<ABC DEF>], [<ABC DEF G H>];

Output:

{}
{ABC}
{ABC and DEF}
{ABC, DEF, G and H}