It's doesn't warn as a result of what you're splitting on, but what you're assigning to. In the olden days, the idiom would look like this:

split;
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which would automatically assign the contents to @_. Maybe the warning should say Implicitly assigning result of split() to @_ is deprecated. I got burned on that one once upon a time, myself.

The reason the second snippet doesn't warn is that you have assigned the result to @chars. I think it's safe to say that the newer behavior is a Good Thing.

As to why the warning doesn't understand that you are still using the results in another context is a little puzzling, something that merlyn can probably answer.

MM

Update: void context =~ scalar context, got it. Thanks japhy!