perl -wle 'use Data::Dumper; my @buckets; my $buckets = 4; @a = 1 .. 14; push @buckets, [ grep defined, @a[ map { $_ * $buckets } 0 .. @a / $buckets ] ] xor shift @a for 1 .. 1 + @a / $buckets; print Dumper( @buckets )'