Joshua ben Jore wrote:
josh@lik:~$ bin/perl/5.9.4/bin/perl5.9.4 -Mwarnings -e '$^V ge "\5\x08\0"'
Useless use of string ge in void context at -e line 1.
Version string ' contains invalid data; ignoring: ' at -e line 1.

$ LD_LIBRARY_PATH=. ./perl -Ilib -MDevel::Peek -we '$v = "\5\x08\0"; Dump($v)'
SV = PV(0x8272040) at 0x8286320
REFCNT = 1
FLAGS = (PK,pPK)
PV = 0x8281048 "\5\10\0"\0
CUR = 3
LEN = 4

I'm kind of stuck here. There is no way for me to know that you have hand
crafted what is equivalent to a v-string without using the magic v-string code
(found in 5.8.1 or better):

$ LD_LIBRARY_PATH=. ./perl -Ilib -MDevel::Peek -we '$v = 5.8.0; Dump($v)'
SV = PVMG(0x82a02b8) at 0x8286320
REFCNT = 1
FLAGS = (RMG,PK,pPK)
IV = 0
NV = 0
PV = 0x8281048 "\5\10\0"\0
CUR = 3
LEN = 4
MAGIC = 0x82a21d8
MG_VIRTUAL = 0
MG_TYPE = PERL_MAGIC_vstring(V)
MG_LEN = 5
MG_PTR = 0x827ce40 "5.8.0"

The only think I can think of doing is to throw in a heuristic like this
(currently only in the pure Perl version.pm release):

# may be a non-magic v-string
if ( $] >= 5.006_002 && $] < 5.008_001
&& length($value) >= 3 && $value !~ /[._]/ ) {
my $tvalue = sprintf("%vd",$value);
if ( $tvalue =~ /^\d+\.\d+\.\d+$/ ) {
# must be a non-magic v-string
$value = $tvalue;
}
}

but that isn't guaranteed to be correct, just highly unlikely to be wrong

John

Joshua ben Jore wrote:
The documentation in perlvar says that $^V stringifies to a string
like C<chr(5) . chr(6) . chr(0)which is nonprintable. perlvar has
said this since 5.6.0 and it still does. I didn't realize it but the
current stringification of $^V in bleadperl is contrary to what's been
documented. Per the docs, $^V eq "\005\011\004" is the correct
response and the "v5.9.4" is the wrong response.

You're right, I should have updated the documentation when I added the
$^V object patch. I made sure that the more common case (of trying to
print out $^V) still worked, even though $^V is now an object:

$ LD_LIBRARY_PATH=. ./perl -e 'printf("%vd",$^V)'
5.9.4

But, to actually quote the documentation:

>$^V The revision, version, and subversion of the Perl interpreter,
represented as a string composed of characters with those ordi-
nals. Thus in Perl v5.6.0 it equals "chr(5) . chr(6) . chr(0)"
and will return true for "$^V eq v5.6.0". Note that the char-
acters in this string value can potentially be in Unicode
range.

This can be used to determine whether the Perl interpreter exe-
cuting a script is in the right range of versions. (Mnemonic:
use ^V for Version Control.) Example:

warn "No \"our\" declarations!\n" if $^V and $^V lt v5.6.0;

Which is all strictly true: in Perl v5.6.0, $^V is the same as "chr(5) .
chr(6) . chr(0)"; it just isn't true in 5.9.x. It is only because you
used the form "\5\x08\0" that anything broke. Had you used the examples
cited (using v-strings), you would never have noticed anything wrong

John

Joshua ben Jore wrote:
I think the documentation used chr(5).chr(6).chr(0) as an example, not
a statement that the behavior was true only in 5.6.0. It certainly
reads that way. I wouldn't have thought that the docs were defining
$^V for the 5.6.0 perl and that the format was undefined for all other
versions. I think this is really splitting hairs if you mean that when
it says the string is chr(5).chr(6).chr(0) it really means that the
only valid way to make that value is v5.6.0.

I /am/ splitting hairs, since I said it was "strictly" true. But you are
still ignoring my point that the actual example of using $^V for
comparison purposes _in_ _the_ _PD_ uses v-strings, which continues to
work with version objects. Believe me, if I had know where the
v-string/version object stuff would have gone, and the totally off the
wall way people have used v-strings in the past, I wouldn't have done
*any* of this work. I've seen things that ordinary humans just weren't
meant to see! ;-)

I think the documentation needs to be altered to eliminate any
discussion of the underlying representation and merely discuss the
correct usage of $^V.

John