[P5P] sprintf, documentation or implementation?

For your interpretation to be consistent, you'd have to expect that to
return " 0", i.e., space prefixed rather than unprefixed.
The documentation is in error: the "positive" should have been
"non-negative". Older versions of perlfunc(1) have "positive" instead of
"non-negative" in the descriptions of the individual flags too. POSIX is
clear (well, if you read it very carefully) that the flags affect zero:

+
The result of a signed conversion shall always begin with a sign
( '+' or '-' ). The conversion shall begin with a sign only when
a negative value is converted if this flag is not specified.
<space>
If the first character of a signed conversion is not a sign or
if a signed conversion results in no characters, a <space> shall
be prefixed to the result. This means that if the <space> and
'+' flags both appear, the <space> flag shall be ignored.

http://www.opengroup.org/onlinepubs/009695399/functions/printf.html

-zefram

Certainly not, see the doc:

"When a space and a plus sign are given as the flags at
once, a plus sign is used to prefix a positive number."

(which means to me that the space is only functional, not displayable,
much like an escape character)

Perl's printf is different.