C:\test>p1
[0]{0} Perl> use Algorithm::Combinatorics qw[ permutations ];;
[0]{0.00943684577941895} Perl> $iter = permutations( [ reverse 1 .. 9 ] );;

[0]{0.000318050384521484} Perl> printf "\r%s\t", join '', @$_ while defined( $_ = $iter->next );;
123456789   
    
[0]{22.5874218940735} Perl>