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+/∧\BA Number of leading ones
∧\' '=CA Mask of leading blanks
+/∧\' '=CA Number of leading blanks

   b←1e6⍴1
   cmpx '+/∧\b' '+/(∧\)b'
  +/∧\b   → 1.66E¯3 |   0% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕
  +/(∧\)b → 1.98E¯4 | -89% ⎕⎕

   c←1e6⍴' '
   i←((⍴c)÷4)⍴bbbb←256⊥4⍴⎕av⍳' '
   bbbb
67372036

   cmpx '∧\'' ''=c' '∧\bbbb=i'
  ∧\' '=c  → 1.00E¯3 |   0% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕
* ∧\bbbb=i → 6.41E¯4 | -36% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕

   cmpx '+/∧\'' ''=c' '+/(∧\)bbbb=i'
  +/∧\' '=c    → 9.31E¯4 |   0% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕
* +/(∧\)bbbb=i → 6.71E¯4 | -28% ⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕⎕