|The stupid question is the question not asked|
Hmm, it looks weird that a boolean switch should accept 1 but not 0. (???)
So I took a look into the documentation. ...
Turns out that SuppressEmpty is not a real flag, but that "" and undef are used to define how empty elements are represented or ignored in a case of a true value.
And the docs explicitly talk about "suppressing the generation of warnings" in XMLout().
I find the naming and concept too error prone.
Something like RepresentEmpty => "off" | "" | undef might have been a better choice.
And I'm understanding even better now, why this module is discouraged, even in its own POD.