I don't have a problem with the implicit split to @_, when called in a void context. It wouldn't do anything useful at all otherwise.

And the number of items produced is then readily availble as scalar @_:

while(<>) {
    split;
    warn "processing " . @_ . " tokens\n";
    &process; # implicitly takes @_
}
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Having split in a scalar context just return the count also makes sense. (To me at least.)