C:\usr\local\share>perl -MAlgorithm::Permute -e "my $p=Algorithm::Permute::->new([1..8],5); while(my @res=$p->next){print qq(@res\n)}"
5 4 3 2 1
4 5 3 2 1
4 3 5 2 1
4 3 2 5 1
4 3 2 1 5
5 3 4 2 1
3 5 4 2 1
3 4 5 2 1
3 4 2 5 1
3 4 2 1 5
...
8 1 2 3 4
1 8 2 3 4
1 2 8 3 4
1 2 3 8 4
1 2 3 4 8