The only specialty about "0 but true" are the missing messages under "warnings".
in reply to Re^3: What is the correct definition of False and Null in Perl?
in thread What is the correct definition of False and Null in Perl?
Yes. That is correct. "0 but true" is a special case that does not emit a warning when used in a numeric expression.
0E0 is the "standard way" of "true but zero".
0.0 is not quite the same as 0E0. The DBI uses 0E0. Ok, maybe 0.0 could have been used, but it wasn't. I think that it is pointless to debate 0E0 vs 0.0, 0E0 has won and so let's go to another question.