sub sxsorta (&;) {
    my $sort_key = shift;
    my @rank = map &$sort_key, @_;
    @_[ sort { $rank[$a] cmp $rank[$b] } 0 .. $#_ ];
}

sub sxsortn (&;) {
    my $sort_key = shift;
    my @rank = map &$sort_key, @_;
    @_[ sort { $rank[$a] <=> $rank[$b] } 0 .. $#_ ];
}