dot ← {⍺ (⍺⍺⌿⍵⍵¨⍤¯1)⍤1 255 ⊢⍵}

   cmpx 'x+.×y' 'x+dot×y'
 x+.×y   → 2.03E¯4 |      0%
 x+dot×y → 5.52E¯2 | +27076% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕

   dot0 ← {⍺ (⍺⍺⌿⍵⍵⍤¯1)⍤1 255 ⊢⍵}

   cmpx 'x+.×y' 'x+dot0×y'
 x+.×y    → 2.08E¯4 |    0% ⎕⎕⎕
 x+dot0×y → 1.68E¯3 | +710% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕


   cmpx 'x{⍺+⍵}.{⍺×⍵}y' 'x{⍺+⍵}dot{⍺×⍵}y'
 x{⍺+⍵}.{⍺×⍵}y   → 3.44E¯1 |   0% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕
 x{⍺+⍵}dot{⍺×⍵}y → 2.72E¯1 | -22% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕