See L<perldata>.
+=head2 Perl's version numbering has changed
+
+Beginning with Perl version 5.6, the version number convention has been
+changed to a "dotted integer" scheme that is more commonly found in open
+source projects.
+
+Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
+The next development series following v5.6 will be numbered v5.7.x,
+beginning with v5.7.0, and the next major production release following
+v5.6 will be v5.8.
+
+The English module now sets $PERL_VERSION to $^V (a string value) rather
+than C<$]> (a numeric value). (This is a potential incompatibility.
+Send us a report via perlbug if you are affected by this.)
+
+The v1.2.3 syntax is also now legal in Perl.
+See L<Support for strings represented as a vector of ordinals> for more on that.
+
+To cope with the new versioning system's use of at least three significant
+digits for each version component, the method used for incrementing the
+subversion number has also changed slightly. We assume that versions older
+than v5.6 have been incrementing the subversion component in multiples of
+10. Versions after v5.6.0 will increment them by 1. Thus, using the new
+notation, 5.005_03 is the same as v5.5.30, and the first maintenance
+version following v5.6.0 will be v5.6.1, which amounts to a floating point
+value of 5.006_001).
+
+=item Literals of the form C<1.2.3> parse differently
+
+Previously, numeric literals with more than one dot in them were
+interpreted as a floating point number concatenated with one or more
+numbers. Such "numbers" are now parsed as strings composed of the
+specified ordinals.
+
+For example, C<print 97.98.99> used to output C<97.9899> in earlier
+versions, but now prints C<abc>.
+
+See L<Support for strings represented as a vector of ordinals> below.
+
=item Possibly changed pseudo-random number generator
In 5.005_0x and earlier, perl's rand() function used the C library
the same effect as assigning C<undef> to the readonly value--it
throws an exception.
-=item Close-on-exec bit may be set on pipe() handles
+=item Close-on-exec bit may be set on pipe and socket handles
On systems that support a close-on-exec flag on filehandles, the
-flag will be set for any handles created by pipe(), if that is
-warranted by the value of $^F that may be in effect. Earlier
-versions neglected to set the flag for handles created with
-pipe(). See L<perlfunc/pipe> and L<perlvar/$^F>.
+flag will be set for any handles created by pipe(), socketpair(),
+socket(), and accept(), if that is warranted by the value of $^F
+that may be in effect. Earlier versions neglected to set the flag
+for handles created with these operators. See L<perlfunc/pipe>,
+L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
+and L<perlvar/$^F>.
=item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
interpreter threads). C<use Thread;> continues to be available when you
ask for -Duse5005threads, bugs and all.
-=head2 Perl's version numbering has changed
-
-Beginning with Perl version 5.6, the version number convention has been
-changed to a "dotted tuple" scheme that is more commonly found in open
-source projects.
-
-Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
-The next development series following v5.6 will be numbered v5.7.x,
-beginning with v5.7.0, and the next major production release following
-v5.6 will be v5.8.
-
-The v1.2.3 syntax is also now legal in Perl. See L<Support for version tuples>
-for more on that.
-
-To cope with the new versioning system's use of at least three significant
-digits for each version component, the method used for incrementing the
-subversion number has also changed slightly. We assume that versions older
-than v5.6 have been incrementing the subversion component in multiples of
-10. Versions after v5.6 will increment them by 1. Thus, using the new
-notation, 5.005_03 is the same as v5.5.30, and the first maintenance
-version following v5.6 will be v5.6.1, which amounts to a floating point
-value of 5.006_001).
-
=head2 New Configure flags
The following new flags may be enabled on the Configure command line
=head2 Unicode and UTF-8 support
Perl can optionally use UTF-8 as its internal representation for character
-strings. The C<utf8> and C<byte> pragmas are used to control this support
-in the current lexical scope. See L<perlunicode>, L<utf8> and L<byte> for
+strings. The C<utf8> and C<bytes> pragmas are used to control this support
+in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
more information.
=head2 Interpreter cloning, threads, and concurrency
the opportunity to introduce typing and other attributes for such
variables. See L<perlfunc/our>.
-=head2 Support for version tuples
+=head2 Support for strings represented as a vector of ordinals
-Literals of the form v1.2.3.4 are now parsed as the utf8 string
-C<"\x{1}\x{2}\x{3}\x{4}">. This allows comparing version numbers using
-regular string comparison operators C<eq>, C<ne>, C<lt>, C<gt> etc.
+Literals of the form C<v1.2.3.4> are now parsed as a string composed of
+of characters with the specified ordinals. This is an alternative, more
+readable way to construct (possibly unicode) strings instead of
+interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
+C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
+parsed the same as C<v1.2.3>.
-These "dotted tuples" are dual-valued. They are both strings of utf8
-characters, and floating point numbers. Thus v1.2.3.4 has the string
-value C<"\x{1}\x{2}\x{3}\x{4}"> and the numeric value 1.002_003_004.
-As another example, v5.5.640 has the string value C<"\x{5}\x{5}\x{280}">
-(remember 280 hexadecimal is 640 decimal) and the numeric value
-5.005_64.
+Strings written in this form are also useful to represent version "numbers".
+It is easy to compare such version "numbers" (which are really just plain
+strings) using any of the usual string comparison operators C<eq>, C<ne>,
+C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
+C<&>, etc.
In conjunction with the new C<$^V> magic variable (which contains
-the perl version in this format), such literals can be used to
-check if you're running a particular version of Perl.
+the perl version as a string), such literals can be used as a readable way
+to check if you're running a particular version of Perl:
+ # this will parse in older versions of Perl also
if ($^V and $^V gt v5.5.640) {
- # new style version numbers are supported
+ # new features supported
}
-C<require> and C<use> also support such literals:
+C<require> and C<use> also have some special magic to support such literals.
+They will be interpreted as a version rather than as a module name:
+
+ require v5.6.0; # croak if $^V lt v5.6.0
+ use v5.6.0; # same, but croaks at compile-time
- require v5.6.0; # croak if $^V lt v5.6.0
- use v5.6.0; # same, but croaks at compile-time
+Alternatively, the C<v> may be omitted if there is more than one dot:
-C<sprintf> and C<printf> support the Perl-specific format type C<%v>
-to print arbitrary strings as dotted tuples.
+ require 5.6.0;
+ use 5.6.0;
- printf "v%v", $^V; # prints current version, such as "v5.5.650"
+Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
+to print ordinals of characters in arbitrary strings:
+
+ printf "v%vd", $^V; # prints current version, such as "v5.5.650"
+ printf "%*vX", ":", $addr; # formats IPv6 address
+ printf "%*vb", " ", $bits; # displays bitstring
+
+See L<perlop/"Strings of Character"> for additional information.
=head2 Weak references
64-bit clean, they are explictly forced to be 32-bit because of
tangled backward compatibility issues. This limitation is subject to
change. Bit arithmetics for bit vector scalars (created by vec()) are
-not limited in their width.
+not limited in their width, you can use the & | ^ ~ operators on such
+scalars.
Last but not least: note that due to Perl's habit of always using
floating point numbers the quads are still not true integers.
=head2 New variable $^V contains Perl version in v5.6.0 format
-C<$^V> contains the Perl version number as a version tuple that
-can be used in string or numeric comparisons. See
-C<Support for version tuples> for an example.
+C<$^V> contains the Perl version number as a string composed of
+characters whose ordinals match the version numbers, so that it may
+be used in string comparisons.
+
+See C<Support for strings represented as a vector of ordinals> for an
+example.
=head2 Optional Y2K warnings
with another number.
This behavior must be specifically enabled when running Configure.
-See L<INSTALL> and L<README.Y2K>.
+See F<INSTALL> and F<README.Y2K>.
=head1 Significant bug fixes
The Devel::Peek module provides access to the internal representation
of Perl variables and data. It is a data debugging tool for the XS programmer.
+=item English
+
+$PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
+(a numeric value).
+
=item ExtUtils::MakeMaker
change#4135, also needs docs in module pod
automatically/transparently added to sysopen() flags if large file
support has been configured), Free/Net/OpenBSD locking behaviour flags
F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
-O_RDONLY, O_WRONLY, and O_RDWR. Also SEEK_SET, SEEK_CUR, and SEEK_END
-added for one-stop shopping of the seek/sysseek constants.
+O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
+SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
+The chmod()/stat() S_IF* constants and S_IS* functions are available
+via the C<:mode> tag.
+
=item File::Compare
my ($foo, $bar) = @_;
-Remember that "my", "our" and "local" bind closer than comma.
+Remember that "my", "our", and "local" bind tighter than comma.
=item Possible Y2K bug: %s
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