The thing is, I think for (@array) is optimized to take a reference to the array rather putting it in list context (similarly to how for (x..y) is optimized not to flatten the list). 

sub f4 {
   for (@_) {
      print($_);
      shift;
   }
   print("\n");
}

sub f5 {
   for ((), @_) {
      print($_);
      shift;
   }
   print("\n");
}

f4(map/./g, Japh);  # Jp
f5(map/./g, Japh);  # Japh

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(Copied from Re^3: For vs. While)

I believe there are 5 kinds of for loops.

In reply to Re^2: Iteration order of a foreach by ikegami
in thread Iteration order of a foreach by Anonymous Monk

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