B::Deparse reported this construct as an empty list

        if ($tmp eq 'F') {
            ();
        }elsif ...
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OK, so is an empty list placed at this point in the bytecode so that when reached, the program evaluates the list? In what context? Or is this just a shorthand display for some NOOP code?

The actual bytecode at this point is a single 'stub' op, whose action is to return undef in a scalar context and nothing otherwise. In your example, it's called in a void context. The empty list happens to compile to the same op.

Dave.