I was already bitten by a case where I wanted to return a list like 1,2,3 from a sub and replaced it with  1..3 which acted differently in scalar context.

True I should have used wantarray, but one intuitively expect a constant behavior...

(I had different code-branches which returned and I didn't want to duplicate wantarray checks for each branch.)

FWIW, here a possible implementation of listify: Re^3: wantarray alternative

Maybe something like l_return (always return list) and a_return (always return array) could help...