x←6 2 3 7 4
   y←9 3 5 8 0 5

   x ∘.× y
54 18 30 48 0 30
18  6 10 16 0 10
27  9 15 24 0 15
63 21 35 56 0 35
36 12 20 32 0 20

54 18 30 48  0 30
   18  6 10 16  0 10
      27  9 15 24  0 15
         63 21 35 56  0 35
            36 12 20 32  0 20

   ptimes ← {+⌿(-⍳⍴⍺)⌽⍺∘.×⍵,0×1↓⍺}

   x ptimes y
54 36 63 130 88 101 86 47 35 20

   carry←{{¯1↓+⌿0 1⌽0,0 10⊤⍵}⍣≡⍵,0}

   carry x ptimes y
4 1 7 6 1 1 7 6 0 4 2

   47326 × 508539
24067116714