I'm not sure what you mean, BUK needs the (&) prototype as syntactic sugar to avoid writing the sub statement to get a coderef like in doit sub {...code ...}

But "disabling prototype checking" leads to another solution of his problem 8)

  DB<8> sub doit (&) { $_[0]->("para") }
 
  DB<9> $codeRef= sub { print @_ }
 
  DB<10> doit {print @_}
para
  DB<11> &doit($codeRef)  # disable checking
para
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