sub serial {
    join(', ', @_[0 .. $#_-1])
    . (@_ > 2 ? ',' : '')
    . (@_ > 1 ? ' and ' : '')
    . $_[-1];
}

##</code><code>##

sub serial {
    my $last = pop;
    join(', ', @_)
    . (@_ > 1 ? ',' : '')
    . (@_ > 0 ? ' and ' : '')
    . $last;
}