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use Algorithm::Loops qw( NestedLoops );

...
while (my @vals = $i->()) {
   print(join(' ', @vals), "\n");
}

use Algorithm::Loops qw( NestedLoops );

...
   my @vals = map { $arr[$_][$idx[$_]] } 0..$#idx;
   print('(', join(',', @idx), ') --> ', join(' ', @vals), "\n");
}