Why not just do away with the local var completely:

@a = ( [1..3],['a'..'c'],['x'..'z']);;

@a = map{ [ map{ shift @$_  } @a ] } 1 .. @{ $a[0] };;

print pp @a;;
([1, "a", "x"], [2, "b", "y"], [3, "c", "z"])
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