You can shorten this:

for $r (@a) {
  $b[$r][$_] = $" for @a }
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To this:

@b = ([($")x@a])x@a;
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You can also shorten this:

print map{ @{$e[$_]}, $/ } @a;
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using the for statment modifier:

print @{$e[$_]}, $/ for @a;
[download]