Assigning to the empty list forces list context upon the RHS.

So does system, but you don't see me using system to force list context. Your code supports what I say:

print ( 'a', 'b', foo );                 # adcde
print +() = ( 'a', 'b', foo );           # nothing
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Assigning to the empty list does more than force context. It's not a good choice to force list context.