Upstile.dyalog

 Upstile←{ ⍝ ⌈ which allows uppercasing letters
     0≠⎕NC'⍺':⍺⌈⍵ ⍝ dyadic case
     2|⎕DR∊⍵:⌈⍵   ⍝ shortcut if all numeric
     w⊣(∊w)←{
         2|⎕DR ⍵:⌈⍵ ⍝ numeric
         11::⍵      ⍝ fallback to no-op
         1(819⌶)⍵   ⍝ uppercase
     }¨∊w←⍵
 }