Your code looks better. Here is one liner. Two ways, filling first bucket first and filling bucket one after another.

$ perl -MData::Dumper -le '$bucket={}; @a=(1..12); $max=scalar @a/4; f
+or my $x(1..4) { for my $y(0..$max-1){ push @{$bucket->{$x}},shift(@a
+); } } print Dumper $bucket'
$VAR1 = {
          '4' => [
                   10,
                   11,
                   12
                 ],
          '1' => [
                   1,
                   2,
                   3
                 ],
          '3' => [
                   7,
                   8,
                   9
                 ],
          '2' => [
                   4,
                   5,
                   6
                 ]
        };


$ perl -MData::Dumper -le '$how_many=4; $bucket={}; $count=1;for (1..1
+2) { push @{$bucket->{$count++}},$_; $count=1 if $_%$how_many == 0; }
+; print Dumper $bucket'
$VAR1 = {
          '2' => [
                   2,
                   6,
                   10
                 ],
          '3' => [
                   3,
                   7,
                   11
                 ],
          '4' => [
                   4,
                   8,
                   12
                 ],
          '1' => [
                   1,
                   5,
                   9
                 ]
        };
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