在Perl中,如何生成列表的所有可能组合？

my @list = <a/>;
print COMBINATIONS($list);

sub COMBINATIONS {
    my ($list) = @_;
    if (scalar(@$list) == 1) {
        return $list;
    } else {
        return COMBINATIONS(grep {$_ != $list->[-1]} @$list);
    }
}

my @list = <a b c d e f g h i j k l m n o p q r s t u v w x y z/>;
print COMBINATIONS($list);

perl -e 'my @list = <a b c d e f g h i j k l m n o p q r s t u v w x y z/>; print COMBINATIONS($list);'