in reply to Permuting with duplicates and no memory

If you want a nice numeric permutation iterator-making closure (as I did), here's how I'd write it (based completely on the above node).
sub make_orderings { my $num = shift; my @arr = (1 .. $num); return sub { my $last = $#arr; my $i = $last - 1; $i-- while 0 <= $i && $arr[$i] >= $arr[$i+1]; return if $i == -1; @arr[$i+1..$last] = reverse @arr[$i+1..$last] if $arr[$i+1] > $arr[$last]; my $j=$i+1; $j++ while $arr[$i] >= $arr[$j]; @arr[$i,$j] = @arr[$j,$i]; return @arr; } }

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