<LI><A HREF="#support for strings represented as a vector of ordinals">Support for strings represented as a vector of ordinals</A></LI>
<LI><A HREF="#improved perl version numbering system">Improved Perl version numbering system</A></LI>
<LI><A HREF="#new syntax for declaring subroutine attributes">New syntax for declaring subroutine attributes</A></LI>
<LI><A HREF="#file and directory handles can be autovivified">File and directory handles can be autovivified</A></LI>
<LI><A HREF="#open() with more than two arguments"><A HREF="../../lib/Pod/perlfunc.html#item_open"><CODE>open()</CODE></A> with more than two arguments</A></LI>
<LI><A HREF="#enhanced support for sort() subroutines">Enhanced support for <A HREF="../../lib/Pod/perlfunc.html#item_sort"><CODE>sort()</CODE></A> subroutines</A></LI>
<LI><A HREF="#pack() format 'z' supported"><A HREF="../../lib/Pod/perlfunc.html#item_pack"><CODE>pack()</CODE></A> format 'Z' supported</A></LI>
<LI><A HREF="#pack() format modifier '!' supported"><A HREF="../../lib/Pod/perlfunc.html#item_pack"><CODE>pack()</CODE></A> format modifier '!' supported</A></LI>
<LI><A HREF="#pack() and unpack() support counted strings"><A HREF="../../lib/Pod/perlfunc.html#item_pack"><CODE>pack()</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_unpack"><CODE>unpack()</CODE></A> support counted strings</A></LI>
<LI><A HREF="#comments in pack() templates">Comments in <A HREF="../../lib/Pod/perlfunc.html#item_pack"><CODE>pack()</CODE></A> templates</A></LI>
<LI><A HREF="#some arrows may be omitted in calls through references">Some arrows may be omitted in calls through references</A></LI>
<LI><A HREF="#boolean assignment operators are legal lvalues">Boolean assignment operators are legal lvalues</A></LI>
<LI><A HREF="#exists() is supported on subroutine names"><A HREF="../../lib/Pod/perlfunc.html#item_exists"><CODE>exists()</CODE></A> is supported on subroutine names</A></LI>
<LI><A HREF="#exists() and delete() are supported on array elements"><A HREF="../../lib/Pod/perlfunc.html#item_exists"><CODE>exists()</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_delete"><CODE>delete()</CODE></A> are supported on array elements</A></LI>
<LI><A HREF="#pseudohashes work better">Pseudo-hashes work better</A></LI>
<LI><A HREF="#automatic flushing of output buffers">Automatic flushing of output buffers</A></LI>
<LI><A HREF="#better diagnostics on meaningless filehandle operations">Better diagnostics on meaningless filehandle operations</A></LI>
<LI><A HREF="#where possible, buffered data discarded from duped input filehandle">Where possible, buffered data discarded from duped input filehandle</A></LI>
<LI><A HREF="#eof() has the same old magic as <>"><A HREF="../../lib/Pod/perlfunc.html#item_eof"><CODE>eof()</CODE></A> has the same old magic as <></A></LI>
<LI><A HREF="#binmode() can be used to set :crlf and :raw modes"><A HREF="../../lib/Pod/perlfunc.html#item_binmode"><CODE>binmode()</CODE></A> can be used to set :crlf and :raw modes</A></LI>
<LI><A HREF="#t filetest recognizes utf8 encoded files as text"><CODE>-T</CODE> filetest recognizes UTF-8 encoded files as ``text''</A></LI>
<LI><A HREF="#system(), backticks and pipe open now reflect exec() failure">system(), backticks and pipe open now reflect <A HREF="../../lib/Pod/perlfunc.html#item_exec"><CODE>exec()</CODE></A> failure</A></LI>
<LI><A HREF="#require and do may be overridden"><A HREF="../../lib/Pod/perlfunc.html#item_require"><CODE>require</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_do"><CODE>do</CODE></A> may be overridden</A></LI>
<LI><A HREF="#$^x variables may now have names longer than one character">$^X variables may now have names longer than one character</A></LI>
<LI><A HREF="#simple sort() using { $a <=> $b } and the like are optimized">Simple <A HREF="../../lib/Pod/perlfunc.html#item_sort"><CODE>sort()</CODE></A> using { $a <=> $b } and the like are optimized</A></LI>
<LI><A HREF="#optimized assignments to lexical variables">Optimized assignments to lexical variables</A></LI>
<LI><A HREF="#thread test failures">Thread test failures</A></LI>
<LI><A HREF="#ebcdic platforms not supported">EBCDIC platforms not supported</A></LI>
<LI><A HREF="#in 64bit hpux the lib/io_multihomed test may hang">In 64-bit HP-UX the lib/io_multihomed test may hang</A></LI>
<LI><A HREF="#nextstep 3.3 posix test failure">NEXTSTEP 3.3 POSIX test failure</A></LI>
<LI><A HREF="#tru64 (aka digital unix, aka dec osf/1) lib/sdbm test failure with gcc">Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with gcc</A></LI>
<LI><A HREF="#unicos/mk cc failures during configure run">UNICOS/mk CC failures during Configure run</A></LI>
<LI><A HREF="#arrow operator and arrays">Arrow operator and arrays</A></LI>
<P>You can now control the granularity of warnings emitted by perl at a finer
level using the <CODE>use warnings</CODE> pragma. <A HREF="../../lib/warnings.html">the warnings manpage</A> and <A HREF="../../lib/Pod/perllexwarn.html">the perllexwarn manpage</A>
have copious documentation on this feature.</P>
<P>
<H2><A NAME="unicode and utf8 support">Unicode and UTF-8 support</A></H2>
<P>Perl now uses UTF-8 as its internal representation for character
strings. The <CODE>utf8</CODE> and <CODE>bytes</CODE> pragmas are used to control this support
in the current lexical scope. See <A HREF="../../lib/Pod/perlunicode.html">the perlunicode manpage</A>, <A HREF="../../lib/utf8.html">the utf8 manpage</A> and <A HREF="../../lib/bytes.html">the bytes manpage</A> for
more information.</P>
<P>This feature is expected to evolve quickly to support some form of I/O
disciplines that can be used to specify the kind of input and output data
(bytes or characters). Until that happens, additional modules from CPAN
will be needed to complete the toolkit for dealing with Unicode.</P>
<PRE>
NOTE: This should be considered an experimental feature. Implementation
details are subject to change.</PRE>
<P>
<H2><A NAME="support for interpolating named characters">Support for interpolating named characters</A></H2>
<P>The new <CODE>\N</CODE> escape interpolates named characters within strings.
For example, <CODE>"Hi! \N{WHITE SMILING FACE}"</CODE> evaluates to a string
<P>An ``our'' declaration introduces a value that can be best understood
as a lexically scoped symbolic alias to a global variable in the
package that was current where the variable was declared. This is
mostly useful as an alternative to the <CODE>vars</CODE> pragma, but also provides
the opportunity to introduce typing and other attributes for such
variables. See <A HREF="../../lib/Pod/perlfunc.html#our">our in the perlfunc manpage</A>.</P>
<P>
<H2><A NAME="support for strings represented as a vector of ordinals">Support for strings represented as a vector of ordinals</A></H2>
<P>Literals of the form <CODE>v1.2.3.4</CODE> are now parsed as a string composed
of characters with the specified ordinals. This is an alternative, more
readable way to construct (possibly unicode) strings instead of
interpolating characters, as in <CODE>"\x{1}\x{2}\x{3}\x{4}"</CODE>. The leading
<CODE>v</CODE> may be omitted if there are more than two ordinals, so <CODE>1.2.3</CODE> is
parsed the same as <CODE>v1.2.3</CODE>.</P>
<P>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 <CODE>eq</CODE>, <CODE>ne</CODE>,
<CODE>lt</CODE>, <CODE>gt</CODE>, etc., or perform bitwise string operations on them using <CODE>|</CODE>,
<CODE>&</CODE>, etc.</P>
<P>In conjunction with the new <CODE>$^V</CODE> magic variable (which contains
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:</P>
<PRE>
# this will parse in older versions of Perl also
if ($^V and $^V gt v5.6.0) {
# new features supported
}</PRE>
<P><A HREF="../../lib/Pod/perlfunc.html#item_require"><CODE>require</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_use"><CODE>use</CODE></A> also have some special magic to support such literals.
They will be interpreted as a version rather than as a module name:</P>
<PRE>
require v5.6.0; # croak if $^V lt v5.6.0
use v5.6.0; # same, but croaks at compile-time</PRE>
<P>Alternatively, the <CODE>v</CODE> may be omitted if there is more than one dot:</P>
<PRE>
require 5.6.0;
use 5.6.0;</PRE>
<P>Also, <A HREF="../../lib/Pod/perlfunc.html#item_sprintf"><CODE>sprintf</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_printf"><CODE>printf</CODE></A> support the Perl-specific format flag <CODE>%v</CODE>
to print ordinals of characters in arbitrary strings:</P>
<PRE>
printf "v%vd", $^V; # prints current version, such as "v5.5.650"
<P>See <A HREF="../../lib/Pod/perldata.html#scalar value constructors">Scalar value constructors in the perldata manpage</A> for additional information.</P>
<P>
<H2><A NAME="improved perl version numbering system">Improved Perl version numbering system</A></H2>
<P>Beginning with Perl version 5.6.0, the version number convention has been
changed to a ``dotted integer'' scheme that is more commonly found in open
source projects.</P>
<P>Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
The next development series following v5.6.0 will be numbered v5.7.x,
beginning with v5.7.0, and the next major production release following
v5.6.0 will be v5.8.0.</P>
<P>The English module now sets $PERL_VERSION to $^V (a string value) rather
than <CODE>$]</CODE> (a numeric value). (This is a potential incompatibility.
Send us a report via perlbug if you are affected by this.)</P>
<P>The v1.2.3 syntax is also now legal in Perl.
See <A HREF="#support for strings represented as a vector of ordinals">Support for strings represented as a vector of ordinals</A> for more on that.</P>
<P>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 v5.6.0 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 should be read as being
equivalent to a floating point value of 5.006_001 in the older format,
stored in <CODE>$]</CODE>).</P>
<P>
<H2><A NAME="new syntax for declaring subroutine attributes">New syntax for declaring subroutine attributes</A></H2>
<P>Formerly, if you wanted to mark a subroutine as being a method call or
as requiring an automatic <A HREF="../../lib/Pod/perlfunc.html#item_lock"><CODE>lock()</CODE></A> when it is entered, you had to declare
that with a <CODE>use attrs</CODE> pragma in the body of the subroutine.
That can now be accomplished with declaration syntax, like this:</P>
<PRE>
sub mymethod : locked method ;
...
sub mymethod : locked method {
...
}</PRE>
<PRE>
sub othermethod :locked :method ;
...
sub othermethod :locked :method {
...
}</PRE>
<P>(Note how only the first <CODE>:</CODE> is mandatory, and whitespace surrounding
the <CODE>:</CODE> is optional.)</P>
<P><EM>AutoSplit.pm</EM> and <EM>SelfLoader.pm</EM> have been updated to keep the attributes
with the stubs they provide. See <A HREF="../../lib/attributes.html">the attributes manpage</A>.</P>
<P>
<H2><A NAME="file and directory handles can be autovivified">File and directory handles can be autovivified</A></H2>
<P>Similar to how constructs such as <CODE>$x->[0]</CODE> autovivify a reference,
<P>Any platform that has 64-bit integers either</P>
<PRE>
(1) natively as longs or ints
(2) via special compiler flags
(3) using long long or int64_t</PRE>
<P>is able to use ``quads'' (64-bit integers) as follows:</P>
<UL>
<LI>
constants (decimal, hexadecimal, octal, binary) in the code
<P></P>
<LI>
arguments to <A HREF="../../lib/Pod/perlfunc.html#item_oct"><CODE>oct()</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_hex"><CODE>hex()</CODE></A>
<P></P>
<LI>
arguments to print(), <A HREF="../../lib/Pod/perlfunc.html#item_printf"><CODE>printf()</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_sprintf"><CODE>sprintf()</CODE></A> (flag prefixes ll, L, q)
<P></P>
<LI>
printed as such
<P></P>
<LI>
<A HREF="../../lib/Pod/perlfunc.html#item_pack"><CODE>pack()</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_unpack"><CODE>unpack()</CODE></A> ``q'' and ``Q'' formats
<P></P>
<LI>
in basic arithmetics: + - * / % (NOTE: operating close to the limits
of the integer values may produce surprising results)
<P></P>
<LI>
in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
to be 32 bits wide but now operate on the full native width.)
<P></P>
<LI>
<A HREF="#item_vec"><CODE>vec()</CODE></A>
<P></P></UL>
<P>Note that unless you have the case (a) you will have to configure
and compile Perl using the -Duse64bitint Configure flag.</P>
<PRE>
NOTE: The Configure flags -Duselonglong and -Duse64bits have been
deprecated. Use -Duse64bitint instead.</PRE>
<P>There are actually two modes of 64-bitness: the first one is achieved
using Configure -Duse64bitint and the second one using Configure
-Duse64bitall. The difference is that the first one is minimal and
the second one maximal. The first works in more places than the second.</P>
<P>The <CODE>use64bitint</CODE> does only as much as is required to get 64-bit
integers into Perl (this may mean, for example, using ``long longs'')
while your memory may still be limited to 2 gigabytes (because your
pointers could still be 32-bit). Note that the name <CODE>64bitint</CODE> does
not imply that your C compiler will be using 64-bit <A HREF="../../lib/Pod/perlfunc.html#item_int"><CODE>int</CODE></A>s (it might,
but it doesn't have to): the <CODE>use64bitint</CODE> means that you will be
able to have 64 bits wide scalar values.</P>
<P>The <CODE>use64bitall</CODE> goes all the way by attempting to switch also
integers (if it can), longs (and pointers) to being 64-bit. This may
create an even more binary incompatible Perl than -Duse64bitint: the
resulting executable may not run at all in a 32-bit box, or you may
have to reboot/reconfigure/rebuild your operating system to be 64-bit
aware.</P>
<P>Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
nor -Duse64bitall.</P>
<P>Last but not least: note that due to Perl's habit of always using
floating point numbers, the quads are still not true integers.
When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
are silently promoted to floating point numbers, after which they will
start losing precision (in their lower digits).</P>
<PRE>
NOTE: 64-bit support is still experimental on most platforms.
Existing support only covers the LP64 data model. In particular, the
LLP64 data model is not yet supported. 64-bit libraries and system
APIs on many platforms have not stabilized--your mileage may vary.</PRE>
<P>If you have filesystems that support ``large files'' (files larger than
2 gigabytes), you may now also be able to create and access them from
Perl.</P>
<PRE>
NOTE: The default action is to enable large file support, if
available on the platform.</PRE>
<P>If the large file support is on, and you have a Fcntl constant
O_LARGEFILE, the O_LARGEFILE is automatically added to the flags
of sysopen().</P>
<P>Beware that unless your filesystem also supports ``sparse files'' seeking
to umpteen petabytes may be inadvisable.</P>
<P>Note that in addition to requiring a proper file system to do large
files you may also need to adjust your per-process (or your
per-system, or per-process-group, or per-user-group) maximum filesize
limits before running Perl scripts that try to handle large files,
especially if you intend to write such files.</P>
<P>Finally, in addition to your process/process group maximum filesize
limits, you may have quota limits on your filesystems that stop you
(your user id or your user group id) from using large files.</P>
<P>Adjusting your process/user/group/file system/operating system limits
is outside the scope of Perl core language. For process limits, you
may try increasing the limits using your shell's limits/limit/ulimit
command before running Perl. The BSD::Resource extension (not
included with the standard Perl distribution) may also be of use, it
offers the getrlimit/setrlimit interface that can be used to adjust
process resource usage limits, including the maximum filesize limit.</P>
<P>
<H2><A NAME="long doubles">Long doubles</A></H2>
<P>In some systems you may be able to use long doubles to enhance the
range and precision of your double precision floating point numbers
(that is, Perl's numbers). Use Configure -Duselongdouble to enable
this support (if it is available).</P>
<P>
<H2><A NAME="more bits">``more bits''</A></H2>
<P>You can ``Configure -Dusemorebits'' to turn on both the 64-bit support
and the long double support.</P>
<P>
<H2><A NAME="enhanced support for sort() subroutines">Enhanced support for <A HREF="../../lib/Pod/perlfunc.html#item_sort"><CODE>sort()</CODE></A> subroutines</A></H2>
<P>Perl subroutines with a prototype of <CODE>($$)</CODE>, and XSUBs in general, can
now be used as sort subroutines. In either case, the two elements to
be compared are passed as normal parameters in @_. See <A HREF="../../lib/Pod/perlfunc.html#sort">sort in the perlfunc manpage</A>.</P>
<P>For unprototyped sort subroutines, the historical behavior of passing
the elements to be compared as the global variables $a and $b remains
<P>The <CODE>qw//</CODE> operator is now evaluated at compile time into a true list
instead of being replaced with a run time call to <A HREF="../../lib/Pod/perlfunc.html#item_split"><CODE>split()</CODE></A>. This
removes the confusing misbehaviour of <CODE>qw//</CODE> in scalar context, which
had inherited that behaviour from split().</P>
<P>Thus:</P>
<PRE>
$foo = ($bar) = qw(a b c); print "$foo|$bar\n";</PRE>
<P>now correctly prints ``3|a'', instead of ``2|a''.</P>
<DL>
<DT><STRONG><A NAME="item_Better_worst%2Dcase_behavior_of_hashes">Better worst-case behavior of hashes</A></STRONG><BR>
<DD>
Small changes in the hashing algorithm have been implemented in
order to improve the distribution of lower order bits in the
hashed value. This is expected to yield better performance on
keys that are repeated sequences.
<P></P></DL>
<P>
<H2><A NAME="pack() format 'z' supported"><A HREF="../../lib/Pod/perlfunc.html#item_pack"><CODE>pack()</CODE></A> format 'Z' supported</A></H2>
<P>The new format type 'Z' is useful for packing and unpacking null-terminated
strings. See <A HREF="../../lib/Pod/perlfunc.html#pack">pack in the perlfunc manpage</A>.</P>
<P>
<H2><A NAME="pack() format modifier '!' supported"><A HREF="../../lib/Pod/perlfunc.html#item_pack"><CODE>pack()</CODE></A> format modifier '!' supported</A></H2>
<P>The new format type modifier '!' is useful for packing and unpacking
native shorts, ints, and longs. See <A HREF="../../lib/Pod/perlfunc.html#pack">pack in the perlfunc manpage</A>.</P>
<P>
<H2><A NAME="pack() and unpack() support counted strings"><A HREF="../../lib/Pod/perlfunc.html#item_pack"><CODE>pack()</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_unpack"><CODE>unpack()</CODE></A> support counted strings</A></H2>
<P>The template character '/' can be used to specify a counted string
type to be packed or unpacked. See <A HREF="../../lib/Pod/perlfunc.html#pack">pack in the perlfunc manpage</A>.</P>
<P>
<H2><A NAME="comments in pack() templates">Comments in <A HREF="../../lib/Pod/perlfunc.html#item_pack"><CODE>pack()</CODE></A> templates</A></H2>
<P>The '#' character in a template introduces a comment up to
end of the line. This facilitates documentation of <A HREF="../../lib/Pod/perlfunc.html#item_pack"><CODE>pack()</CODE></A>
See <A HREF="../../lib/Pod/perlsub.html#lvalue subroutines">Lvalue subroutines in the perlsub manpage</A>.</P>
<PRE>
NOTE: This is an experimental feature. Details are subject to change.</PRE>
<P>
<H2><A NAME="some arrows may be omitted in calls through references">Some arrows may be omitted in calls through references</A></H2>
<P>Perl now allows the arrow to be omitted in many constructs
involving subroutine calls through references. For example,
<CODE>$foo[10]->('foo')</CODE> may now be written <CODE>$foo[10]('foo')</CODE>.
This is rather similar to how the arrow may be omitted from
<CODE>$foo[10]->{'foo'}</CODE>. Note however, that the arrow is still
required for <CODE>foo(10)->('bar')</CODE>.</P>
<P>
<H2><A NAME="boolean assignment operators are legal lvalues">Boolean assignment operators are legal lvalues</A></H2>
<P>Constructs such as <CODE>($a ||= 2) += 1</CODE> are now allowed.</P>
<P>
<H2><A NAME="exists() is supported on subroutine names"><A HREF="../../lib/Pod/perlfunc.html#item_exists"><CODE>exists()</CODE></A> is supported on subroutine names</A></H2>
<P>The <A HREF="../../lib/Pod/perlfunc.html#item_exists"><CODE>exists()</CODE></A> builtin now works on subroutine names. A subroutine
is considered to exist if it has been declared (even if implicitly).
See <A HREF="../../lib/Pod/perlfunc.html#exists">exists in the perlfunc manpage</A> for examples.</P>
<P>
<H2><A NAME="exists() and delete() are supported on array elements"><A HREF="../../lib/Pod/perlfunc.html#item_exists"><CODE>exists()</CODE></A> and <A HREF="#item_delete"><CODE>delete()</CODE></A> are supported on array elements</A></H2>
<P>The <A HREF="../../lib/Pod/perlfunc.html#item_exists"><CODE>exists()</CODE></A> and <A HREF="#item_delete"><CODE>delete()</CODE></A> builtins now work on simple arrays as well.
The behavior is similar to that on hash elements.</P>
<P><A HREF="../../lib/Pod/perlfunc.html#item_exists"><CODE>exists()</CODE></A> can be used to check whether an array element has been
initialized. This avoids autovivifying array elements that don't exist.
If the array is tied, the <CODE>EXISTS()</CODE> method in the corresponding tied
package will be invoked.</P>
<P><A HREF="#item_delete"><CODE>delete()</CODE></A> may be used to remove an element from the array and return
it. The array element at that position returns to its unintialized
state, so that testing for the same element with <A HREF="../../lib/Pod/perlfunc.html#item_exists"><CODE>exists()</CODE></A> will return
false. If the element happens to be the one at the end, the size of
the array also shrinks up to the highest element that tests true for
exists(), or 0 if none such is found. If the array is tied, the <CODE>DELETE()</CODE>
method in the corresponding tied package will be invoked.</P>
<P>See <A HREF="../../lib/Pod/perlfunc.html#exists">exists in the perlfunc manpage</A> and <A HREF="../../lib/Pod/perlfunc.html#delete">delete in the perlfunc manpage</A> for examples.</P>
<P>
<H2><A NAME="pseudohashes work better">Pseudo-hashes work better</A></H2>
<P>Dereferencing some types of reference values in a pseudo-hash,
such as <CODE>$ph->{foo}[1]</CODE>, was accidentally disallowed. This has
been corrected.</P>
<P>When applied to a pseudo-hash element, <A HREF="../../lib/Pod/perlfunc.html#item_exists"><CODE>exists()</CODE></A> now reports whether
the specified value exists, not merely if the key is valid.</P>
<P><A HREF="#item_delete"><CODE>delete()</CODE></A> now works on pseudo-hashes. When given a pseudo-hash element
or slice it deletes the values corresponding to the keys (but not the keys
themselves). See <A HREF="../../lib/Pod/perlref.html#pseudohashes: using an array as a hash">Pseudo-hashes: Using an array as a hash in the perlref manpage</A>.</P>
<P>Pseudo-hash slices with constant keys are now optimized to array lookups
at compile-time.</P>
<P>List assignments to pseudo-hash slices are now supported.</P>
<P>The <CODE>fields</CODE> pragma now provides ways to create pseudo-hashes, via
fields::new() and fields::phash(). See <A HREF="../../lib/fields.html">the fields manpage</A>.</P>
<PRE>
NOTE: The pseudo-hash data type continues to be experimental.
Limiting oneself to the interface elements provided by the
fields pragma will provide protection from any future changes.</PRE>
<P>
<H2><A NAME="automatic flushing of output buffers">Automatic flushing of output buffers</A></H2>
<P>fork(), exec(), system(), qx//, and pipe open()s now flush buffers
of all files opened for output when the operation was attempted. This
mostly eliminates confusing buffering mishaps suffered by users unaware
of how Perl internally handles I/O.</P>
<P>This is not supported on some platforms like Solaris where a suitably
correct implementation of <CODE>fflush(NULL)</CODE> isn't available.</P>
<P>
<H2><A NAME="better diagnostics on meaningless filehandle operations">Better diagnostics on meaningless filehandle operations</A></H2>
<P>Constructs such as <A HREF="#item_open"><CODE>open(<FH>)</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_close"><CODE>close(<FH>)</CODE></A>
are compile time errors. Attempting to read from filehandles that
were opened only for writing will now produce warnings (just as
writing to read-only filehandles does).</P>
<P>
<H2><A NAME="where possible, buffered data discarded from duped input filehandle">Where possible, buffered data discarded from duped input filehandle</A></H2>
<P><A HREF="#item_open"><CODE>open(NEW, "<&OLD")</CODE></A> now attempts to discard any data that
was previously read and buffered in <CODE>OLD</CODE> before duping the handle.
On platforms where doing this is allowed, the next read operation
on <CODE>NEW</CODE> will return the same data as the corresponding operation
on <CODE>OLD</CODE>. Formerly, it would have returned the data from the start
of the following disk block instead.</P>
<P>
<H2><A NAME="eof() has the same old magic as <>"><A HREF="../../lib/Pod/perlfunc.html#item_eof"><CODE>eof()</CODE></A> has the same old magic as <></A></H2>
<P><A HREF="../../lib/Pod/perlfunc.html#item_eof"><CODE>eof()</CODE></A> would return true if no attempt to read from <CODE><></CODE> had
yet been made. <A HREF="../../lib/Pod/perlfunc.html#item_eof"><CODE>eof()</CODE></A> has been changed to have a little magic of its
own, it now opens the <CODE><></CODE> files.</P>
<P>
<H2><A NAME="binmode() can be used to set :crlf and :raw modes"><A HREF="../../lib/Pod/perlfunc.html#item_binmode"><CODE>binmode()</CODE></A> can be used to set :crlf and :raw modes</A></H2>
<P><A HREF="../../lib/Pod/perlfunc.html#item_binmode"><CODE>binmode()</CODE></A> now accepts a second argument that specifies a discipline
for the handle in question. The two pseudo-disciplines ``:raw'' and
``:crlf'' are currently supported on DOS-derivative platforms.
See <A HREF="../../lib/Pod/perlfunc.html#binmode">binmode in the perlfunc manpage</A> and <A HREF="../../lib/open.html">the open manpage</A>.</P>
<P>
<H2><A NAME="t filetest recognizes utf8 encoded files as text"><CODE>-T</CODE> filetest recognizes UTF-8 encoded files as ``text''</A></H2>
<P>The algorithm used for the <CODE>-T</CODE> filetest has been enhanced to
correctly identify UTF-8 content as ``text''.</P>
<P>
<H2><A NAME="system(), backticks and pipe open now reflect exec() failure">system(), backticks and pipe open now reflect <A HREF="../../lib/Pod/perlfunc.html#item_exec"><CODE>exec()</CODE></A> failure</A></H2>
<P>On Unix and similar platforms, system(), <A HREF="../../lib/Pod/perlfunc.html#item_qx"><CODE>qx()</CODE></A> and open(FOO, ``cmd |'')
etc., are implemented via <A HREF="../../lib/Pod/perlfunc.html#item_fork"><CODE>fork()</CODE></A> and exec(). When the underlying
<A HREF="../../lib/Pod/perlfunc.html#item_exec"><CODE>exec()</CODE></A> fails, earlier versions did not report the error properly,
since the <A HREF="../../lib/Pod/perlfunc.html#item_exec"><CODE>exec()</CODE></A> happened to be in a different process.</P>
<P>The child process now communicates with the parent about the
error in launching the external command, which allows these
constructs to return with their usual error value and set $!.</P>
On systems that support a close-on-exec flag on filehandles, the
flag is now 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 <A HREF="../../lib/Pod/perlfunc.html#pipe">pipe in the perlfunc manpage</A>,
<A HREF="../../lib/Pod/perlfunc.html#socketpair">socketpair in the perlfunc manpage</A>, <A HREF="../../lib/Pod/perlfunc.html#socket">socket in the perlfunc manpage</A>, <A HREF="../../lib/Pod/perlfunc.html#accept">accept in the perlfunc manpage</A>,
and <A HREF="../../lib/Pod/perlvar.html#$^f">$^F in the perlvar manpage</A>.
Bareword prototypes have been rationalized to enable them to be used
to override builtins that accept barewords and interpret them in
a special way, such as <A HREF="../../lib/Pod/perlfunc.html#item_require"><CODE>require</CODE></A> or <A HREF="../../lib/Pod/perlfunc.html#item_do"><CODE>do</CODE></A>.
<P>Arguments prototyped as <CODE>*</CODE> will now be visible within the subroutine
as either a simple scalar or as a reference to a typeglob.
See <A HREF="../../lib/Pod/perlsub.html#prototypes">Prototypes in the perlsub manpage</A>.</P>
<P></P></DL>
<P>
<H2><A NAME="require and do may be overridden"><A HREF="../../lib/Pod/perlfunc.html#item_require"><CODE>require</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_do"><CODE>do</CODE></A> may be overridden</A></H2>
<P><A HREF="../../lib/Pod/perlfunc.html#item_require"><CODE>require</CODE></A> and <CODE>do 'file'</CODE> operations may be overridden locally
by importing subroutines of the same name into the current package
(or globally by importing them into the CORE::GLOBAL:: namespace).
Overriding <A HREF="../../lib/Pod/perlfunc.html#item_require"><CODE>require</CODE></A> will also affect <A HREF="../../lib/Pod/perlfunc.html#item_use"><CODE>use</CODE></A>, provided the override
is visible at compile-time.
See <A HREF="../../lib/Pod/perlsub.html#overriding builtin functions">Overriding Built-in Functions in the perlsub manpage</A>.</P>
<P>
<H2><A NAME="$^x variables may now have names longer than one character">$^X variables may now have names longer than one character</A></H2>
<P>Formerly, $^X was synonymous with ${``\cX''}, but $^XY was a syntax
error. Now variable names that begin with a control character may be
arbitrarily long. However, for compatibility reasons, these variables
<EM>must</EM> be written with explicit braces, as <CODE>${^XY}</CODE> for example.
<CODE>${^XYZ}</CODE> is synonymous with ${``\cXYZ''}. Variable names with more
than one control character, such as <CODE>${^XY^Z}</CODE>, are illegal.</P>
<P>The old syntax has not changed. As before, `^X' may be either a
literal control-X character or the two-character sequence `caret' plus
`X'. When braces are omitted, the variable name stops after the
control character. Thus <CODE>"$^XYZ"</CODE> continues to be synonymous with
<CODE>$^X . "YZ"</CODE> as before.</P>
<P>As before, lexical variables may not have names beginning with control
characters. As before, variables whose names begin with a control
character are always forced to be in package `main'. All such variables
are reserved for future extensions, except those that begin with
<CODE>^_</CODE>, which may be used by user programs and are guaranteed not to
acquire special meaning in any future version of Perl.</P>
Getopt::Long licensing has changed to allow the Perl Artistic License
as well as the GPL. It used to be GPL only, which got in the way of
non-GPL applications that wanted to use Getopt::Long.
<P>Getopt::Long encourages the use of Pod::Usage to produce help
messages. For example:</P>
<PRE>
use Getopt::Long;
use Pod::Usage;
my $man = 0;
my $help = 0;
GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
pod2usage(1) if $help;
pod2usage(-exitstatus => 0, -verbose => 2) if $man;</PRE>
<PRE>
__END__</PRE>
<PRE>
=head1 NAME</PRE>
<PRE>
sample - Using GetOpt::Long and Pod::Usage</PRE>
<PRE>
=head1 SYNOPSIS</PRE>
<PRE>
sample [options] [file ...]</PRE>
<PRE>
Options:
-help brief help message
-man full documentation</PRE>
<PRE>
=head1 OPTIONS</PRE>
<PRE>
=over 8</PRE>
<PRE>
=item B<-help></PRE>
<PRE>
Print a brief help message and exits.</PRE>
<PRE>
=item B<-man></PRE>
<PRE>
Prints the manual page and exits.</PRE>
<PRE>
=back</PRE>
<PRE>
=head1 DESCRIPTION</PRE>
<PRE>
B<This program> will read the given input file(s) and do someting
useful with the contents thereof.</PRE>
<PRE>
=cut</PRE>
<P>See <A HREF="../../lib/Pod/Usage.html">the Pod::Usage manpage</A> for details.</P>
<P>A bug that prevented the non-option call-back <> from being
specified as the first argument has been fixed.</P>
<P>To specify the characters < and > as option starters, use ><. Note,
however, that changing option starters is strongly deprecated.</P>
<P></P>
<DT><STRONG><A NAME="item_IO">IO</A></STRONG><BR>
<DD>
<A HREF="../../lib/Pod/perlfunc.html#item_write"><CODE>write()</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_syswrite"><CODE>syswrite()</CODE></A> will now accept a single-argument
form of the call, for consistency with Perl's syswrite().
<P>You can now create a TCP-based IO::Socket::INET without forcing
a connect attempt. This allows you to configure its options
(like making it non-blocking) and then call <A HREF="../../lib/Pod/perlfunc.html#item_connect"><CODE>connect()</CODE></A> manually.</P>
<P>A bug that prevented the IO::Socket::protocol() accessor
from ever returning the correct value has been corrected.</P>
<P>IO::Socket::connect now uses non-blocking IO instead of <A HREF="../../lib/Pod/perlfunc.html#item_alarm"><CODE>alarm()</CODE></A>
to do connect timeouts.</P>
<P>IO::Socket::accept now uses <A HREF="../../lib/Pod/perlfunc.html#item_select"><CODE>select()</CODE></A> instead of <A HREF="../../lib/Pod/perlfunc.html#item_alarm"><CODE>alarm()</CODE></A> for doing
timeouts.</P>
<P>IO::Socket::INET->new now sets $! correctly on failure. $@ is
Pod::Parser is a base class for parsing and selecting sections of
pod documentation from an input stream. This module takes care of
identifying pod paragraphs and commands in the input and hands off the
parsed paragraphs and commands to user-defined methods which are free
to interpret or translate them as they see fit.
<P>Pod::InputObjects defines some input objects needed by Pod::Parser, and
for advanced users of Pod::Parser that need more about a command besides
its name and text.</P>
<P>As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned
``base parser code'' recommended for use by all pod2xxx translators.
Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
underway. For any questions or comments about pod parsing and translating
issues and utilities, please use the <A HREF="mailto:pod-people@perl.org">pod-people@perl.org</A> mailing list.</P>
<P>For further information, please see <A HREF="../../lib/Pod/Parser.html">the Pod::Parser manpage</A> and <A HREF="../../lib/Pod/InputObjects.html">the Pod::InputObjects manpage</A>.</P>
A new feature called ``DBM Filters'' has been added to all the
DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
DBM Filters add four new methods to each DBM module:
<PRE>
filter_store_key
filter_store_value
filter_fetch_key
filter_fetch_value</PRE>
<P>These can be used to filter key-value pairs before the pairs are
written to the database or just after they are read from the database.
See <A HREF="../../lib/Pod/perldbmfilter.html">the perldbmfilter manpage</A> for further information.</P>
<P></P></DL>
<P>
<H2><A NAME="pragmata">Pragmata</A></H2>
<P><CODE>use attrs</CODE> is now obsolete, and is only provided for
backward-compatibility. It's been replaced by the <CODE>sub : attributes</CODE>
syntax. See <A HREF="../../lib/Pod/perlsub.html#subroutine attributes">Subroutine Attributes in the perlsub manpage</A> and <A HREF="../../lib/attributes.html">the attributes manpage</A>.</P>
<P>Lexical warnings pragma, <CODE>use warnings;</CODE>, to control optional warnings.
See <A HREF="../../lib/Pod/perllexwarn.html">the perllexwarn manpage</A>.</P>
<P><CODE>use filetest</CODE> to control the behaviour of filetests (<CODE>-r</CODE> <CODE>-w</CODE>
...). Currently only one subpragma implemented, ``use filetest
'access';'', that uses <CODE>access(2)</CODE> or equivalent to check permissions
instead of using <A HREF="../../lib/Pod/perlfunc.html#item_stat"><CODE>stat(2)</CODE></A> as usual. This matters in filesystems
where there are ACLs (access control lists): the <A HREF="../../lib/Pod/perlfunc.html#item_stat"><CODE>stat(2)</CODE></A> might lie,
but <CODE>access(2)</CODE> knows better.</P>
<P>The <A HREF="#item_open"><CODE>open</CODE></A> pragma can be used to specify default disciplines for
handle constructors (e.g. <A HREF="#item_open"><CODE>open())</CODE></A> and for qx//. The two
pseudo-disciplines <CODE>:raw</CODE> and <CODE>:crlf</CODE> are currently supported on
DOS-derivative platforms (i.e. where binmode is not a no-op).
See also <A HREF="#binmode() can be used to set :crlf and :raw modes">binmode() can be used to set :crlf and :raw modes</A>.</P>
<H2><A NAME="simple sort() using { $a <=> $b } and the like are optimized">Simple <A HREF="../../lib/Pod/perlfunc.html#item_sort"><CODE>sort()</CODE></A> using { $a <=> $b } and the like are optimized</A></H2>
<P>Many common <A HREF="../../lib/Pod/perlfunc.html#item_sort"><CODE>sort()</CODE></A> operations using a simple inlined block are now
optimized for faster performance.</P>
<P>
<H2><A NAME="optimized assignments to lexical variables">Optimized assignments to lexical variables</A></H2>
<P>Certain operations in the RHS of assignment statements have been
optimized to directly set the lexical variable on the LHS,
<P>Minor changes in how subroutine calls are handled internally
provide marginal improvements in performance.</P>
<DL>
<DT><STRONG><A NAME="item_delete">delete(), each(), <A HREF="../../lib/Pod/perlfunc.html#item_values"><CODE>values()</CODE></A> and hash iteration are faster</A></STRONG><BR>
<DD>
The hash values returned by delete(), each(), <A HREF="../../lib/Pod/perlfunc.html#item_values"><CODE>values()</CODE></A> and hashes in a
list context are the actual values in the hash, instead of copies.
This results in significantly better performance, because it eliminates
needless copying in most situations.
<P></P></DL>
<P>
<HR>
<H1><A NAME="installation and configuration improvements">Installation and Configuration Improvements</A></H1>
<P>
<H2><A NAME="dusethreads means something different">-Dusethreads means something different</A></H2>
<P>The -Dusethreads flag now enables the experimental interpreter-based thread
support by default. To get the flavor of experimental threads that was in
5.005 instead, you need to run Configure with ``-Dusethreads -Duse5005threads''.</P>
<P>As of v5.6.0, interpreter-threads support is still lacking a way to
create new threads from Perl (i.e., <CODE>use Thread;</CODE> will not work with
interpreter threads). <CODE>use Thread;</CODE> continues to be available when you
specify the -Duse5005threads option to Configure, bugs and all.</P>
<PRE>
NOTE: Support for threads continues to be an experimental feature.
Interfaces and implementation are subject to sudden and drastic changes.</PRE>
<P>Support for this EBCDIC platform has not been renewed in this release.
There are difficulties in reconciling Perl's standardization on UTF-8
as its internal representation for characters with the EBCDIC character
set, because the two are incompatible.</P>
<P>It is unclear whether future versions will renew support for this
platform, but the possibility exists.</P>
<P>
<H2><A NAME="vms">VMS</A></H2>
<P>Numerous revisions and extensions to configuration, build, testing, and
installation process to accomodate core changes and VMS-specific options.</P>
<P>Expand %ENV-handling code to allow runtime mapping to logical names,
CLI symbols, and CRTL environ array.</P>
<P>Extension of subprocess invocation code to accept filespecs as command
``verbs''.</P>
<P>Add to Perl command line processing the ability to use default file types and
to recognize Unix-style <CODE>2>&1</CODE>.</P>
<P>Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.</P>
<P>Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.</P>
<P>Barewords at start of Unix-syntax paths may be treated as text rather than
only as logical names.</P>
<P>Optional secure translation of several logical names used internally by Perl.</P>
<P>Miscellaneous bugfixing and porting of new core code to VMS.</P>
<P>Thanks are gladly extended to the many people who have contributed VMS
patches, testing, and ideas.</P>
<P>
<H2><A NAME="win32">Win32</A></H2>
<P>Perl can now emulate <A HREF="../../lib/Pod/perlfunc.html#item_fork"><CODE>fork()</CODE></A> internally, using multiple interpreters running
in different concurrent threads. This support must be enabled at build
time. See <A HREF="../../lib/Pod/perlfork.html">the perlfork manpage</A> for detailed information.</P>
<P>When given a pathname that consists only of a drivename, such as <CODE>A:</CODE>,
<A HREF="../../lib/Pod/perlfunc.html#item_opendir"><CODE>opendir()</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_stat"><CODE>stat()</CODE></A> now use the current working directory for the drive
rather than the drive root.</P>
<P>The builtin XSUB functions in the Win32:: namespace are documented. See
<P>$^X now contains the full path name of the running executable.</P>
<P>A Win32::GetLongPathName() function is provided to complement
Win32::GetFullPathName() and Win32::GetShortPathName(). See <A HREF="../../lib/Pod/Win32.html">the Win32 manpage</A>.</P>
<P>POSIX::uname() is supported.</P>
<P><A HREF="../../lib/Pod/perlfunc.html#item_system"><CODE>system(1,...)</CODE></A> now returns true process IDs rather than process
handles. <A HREF="../../lib/Pod/perlfunc.html#item_kill"><CODE>kill()</CODE></A> accepts any real process id, rather than strictly
return values from system(1,...).</P>
<P>For better compatibility with Unix, <A HREF="../../lib/Pod/perlfunc.html#item_kill"><CODE>kill(0, $pid)</CODE></A> can now be used to
test whether a process exists.</P>
<P>The <CODE>Shell</CODE> module is supported.</P>
<P>Better support for building Perl under command.com in Windows 95
has been added.</P>
<P>Scripts are read in binary mode by default to allow ByteLoader (and
the filter mechanism in general) to work properly. For compatibility,
the DATA filehandle will be set to text mode if a carriage return is
detected at the end of the line containing the __END__ or __DATA__
token; if not, the DATA filehandle will be left open in binary mode.
Earlier versions always opened the DATA filehandle in text mode.</P>
<P>The <A HREF="../../lib/Pod/perlfunc.html#item_glob"><CODE>glob()</CODE></A> operator is implemented via the <A HREF="#item_File%3A%3AGlob"><CODE>File::Glob</CODE></A> extension,
which supports glob syntax of the C shell. This increases the flexibility
of the <A HREF="../../lib/Pod/perlfunc.html#item_glob"><CODE>glob()</CODE></A> operator, but there may be compatibility issues for
programs that relied on the older globbing syntax. If you want to
preserve compatibility with the older syntax, you might want to run
perl with <CODE>-MFile::DosGlob</CODE>. For details and compatibility information,
see <A HREF="../../lib/File/Glob.html">the File::Glob manpage</A>.</P>
<P>Line numbers (as reflected by <A HREF="../../lib/Pod/perlfunc.html#item_caller"><CODE>caller()</CODE></A> and most diagnostics) within
<CODE>eval '...'</CODE> were often incorrect where here documents were involved.
This has been corrected.</P>
<P>Lexical lookups for variables appearing in <CODE>eval '...'</CODE> within
functions that were themselves called within an <CODE>eval '...'</CODE> were
searching the wrong place for lexicals. The lexical search now
correctly ends at the subroutine's block boundary.</P>
<P>The use of <A HREF="../../lib/Pod/perlfunc.html#item_return"><CODE>return</CODE></A> within <A HREF="../../lib/Pod/perlfunc.html#item_eval"><CODE>eval {...}</CODE></A> caused $@ not to be reset
correctly when no exception occurred within the eval. This has
been fixed.</P>
<P>Parsing of here documents used to be flawed when they appeared as
the replacement expression in <CODE>eval 's/.../.../e'</CODE>. This has
been fixed.</P>
<P>
<H2><A NAME="all compilation errors are true errors">All compilation errors are true errors</A></H2>
<P>Some ``errors'' encountered at compile time were by neccessity
generated as warnings followed by eventual termination of the
program. This enabled more such errors to be reported in a
single run, rather than causing a hard stop at the first error
that was encountered.</P>
<P>The mechanism for reporting such errors has been reimplemented
to queue compile-time errors and report them at the end of the
compilation as true errors rather than as warnings. This fixes
cases where error messages leaked through in the form of warnings
when code was compiled at run time using <A HREF="../../lib/Pod/perlfunc.html#item_eval"><CODE>eval STRING</CODE></A>, and
also allows such errors to be reliably trapped using <CODE>eval "..."</CODE>.</P>
<P>
<H2><A NAME="implicitly closed filehandles are safer">Implicitly closed filehandles are safer</A></H2>
<P>Sometimes implicitly closed filehandles (as when they are localized,
and Perl automatically closes them on exiting the scope) could
inadvertently set $? or $!. This has been corrected.</P>
<P>
<H2><A NAME="behavior of list slices is more consistent">Behavior of list slices is more consistent</A></H2>
<P>When taking a slice of a literal list (as opposed to a slice of
an array or hash), Perl used to return an empty list if the
result happened to be composed of all undef values.</P>
<P>The new behavior is to produce an empty list if (and only if)
the original list was empty. Consider the following example:</P>
<PRE>
@a = (1,undef,undef,2)[2,1,2];</PRE>
<P>The old behavior would have resulted in @a having no elements.
The new behavior ensures it has three undefined elements.</P>
<P>Note in particular that the behavior of slices of the following
<P><A HREF="../../lib/Pod/perlfunc.html#item_printf"><CODE>printf()</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_sprintf"><CODE>sprintf()</CODE></A> previously reset the numeric locale
back to the default ``C'' locale. This has been fixed.</P>
<P>Numbers formatted according to the local numeric locale
(such as using a decimal comma instead of a decimal dot) caused
``isn't numeric'' warnings, even while the operations accessing
those numbers produced correct results. These warnings have been
discontinued.</P>
<P>
<H2><A NAME="memory leaks">Memory leaks</A></H2>
<P>The <CODE>eval 'return sub {...}'</CODE> construct could sometimes leak
memory. This has been fixed.</P>
<P>Operations that aren't filehandle constructors used to leak memory
when used on invalid filehandles. This has been fixed.</P>
<P>Constructs that modified <CODE>@_</CODE> could fail to deallocate values
in <CODE>@_</CODE> and thus leak memory. This has been corrected.</P>
<P>
<H2><A NAME="spurious subroutine stubs after failed subroutine calls">Spurious subroutine stubs after failed subroutine calls</A></H2>
<P>Perl could sometimes create empty subroutine stubs when a
subroutine was not found in the package. Such cases stopped
later method lookups from progressing into base packages.
This has been corrected.</P>
<P>
<H2><A NAME="taint failures under u">Taint failures under <CODE>-U</CODE></A></H2>
<P>When running in unsafe mode, taint violations could sometimes
cause silent failures. This has been fixed.</P>
<P>
<H2><A NAME="end blocks and the c switch">END blocks and the <CODE>-c</CODE> switch</A></H2>
<P>Prior versions used to run BEGIN <STRONG>and</STRONG> END blocks when Perl was
run in compile-only mode. Since this is typically not the expected
behavior, END blocks are not executed anymore when the <CODE>-c</CODE> switch
is used.</P>
<P>See <A HREF="#check blocks">CHECK blocks</A> for how to run things when the compile phase ends.</P>
<P>
<H2><A NAME="potential to leak data filehandles">Potential to leak DATA filehandles</A></H2>
<P>Using the <CODE>__DATA__</CODE> token creates an implicit filehandle to
the file that contains the token. It is the program's
responsibility to close it when it is done reading from it.</P>
<P>This caveat is now better explained in the documentation.
See <A HREF="../../lib/Pod/perldata.html">the perldata manpage</A>.</P>
<P>
<HR>
<H1><A NAME="new or changed diagnostics">New or Changed Diagnostics</A></H1>
<DL>
<DT><STRONG><A NAME="item_%22%25s%22_variable_%25s_masks_earlier_declaration">``%s'' variable %s masks earlier declaration in same %s</A></STRONG><BR>
<DD>
(W misc) A ``my'' or ``our'' variable has been redeclared in the current scope or statement,
effectively eliminating all access to the previous instance. This is almost
always a typographical error. Note that the earlier variable will still exist
until the end of the scope or until all closure referents to it are
destroyed.
<P></P>
<DT><STRONG><A NAME="item_%22my_sub%22_not_yet_implemented">``my sub'' not yet implemented</A></STRONG><BR>
<DD>
(F) Lexically scoped subroutines are not yet implemented. Don't try that
(W misc) You seem to have already declared the same global once before in the
current lexical scope.
<P></P>
<DT><STRONG><A NAME="item_%27%21%27_allowed_only_after_types_%25s">'!' allowed only after types %s</A></STRONG><BR>
<DD>
(F) The '!' is allowed in <A HREF="../../lib/Pod/perlfunc.html#item_pack"><CODE>pack()</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_unpack"><CODE>unpack()</CODE></A> only after certain types.
See <A HREF="../../lib/Pod/perlfunc.html#pack">pack in the perlfunc manpage</A>.
<P></P>
<DT><STRONG><A NAME="item_%2F_cannot_take_a_count">/ cannot take a count</A></STRONG><BR>
<DD>
(F) You had an unpack template indicating a counted-length string,
but you have also specified an explicit size for the string.
See <A HREF="../../lib/Pod/perlfunc.html#pack">pack in the perlfunc manpage</A>.
<P></P>
<DT><STRONG><A NAME="item_%2F_must_be_followed_by_a%2C_A_or_Z">/ must be followed by a, A or Z</A></STRONG><BR>
<DD>
(F) You had an unpack template indicating a counted-length string,
which must be followed by one of the letters a, A or Z
to indicate what sort of string is to be unpacked.
See <A HREF="../../lib/Pod/perlfunc.html#pack">pack in the perlfunc manpage</A>.
<P></P>
<DT><STRONG><A NAME="item_%2F_must_be_followed_by_a%2A%2C_A%2A_or_Z%2A">/ must be followed by a*, A* or Z*</A></STRONG><BR>
<DD>
(F) You had a pack template indicating a counted-length string,
Currently the only things that can have their length counted are a*, A* or Z*.
See <A HREF="../../lib/Pod/perlfunc.html#pack">pack in the perlfunc manpage</A>.
<P></P>
<DT><STRONG><A NAME="item_%2F_must_follow_a_numeric_type">/ must follow a numeric type</A></STRONG><BR>
<DD>
(F) You had an unpack template that contained a '#',
but this did not follow some numeric unpack specification.
See <A HREF="../../lib/Pod/perlfunc.html#pack">pack in the perlfunc manpage</A>.
(W regexp) You used a backslash-character combination which is not recognized
by Perl. This combination appears in an interpolated variable or a
<CODE>'</CODE>-delimited regular expression. The character was understood literally.
<P></P>
<DT><STRONG><A NAME="item_%2F%25s%2F%3A_Unrecognized_escape_%5C%5C%25c_in_ch">/%s/: Unrecognized escape \\%c in character class passed through</A></STRONG><BR>
<DD>
(W regexp) You used a backslash-character combination which is not recognized
by Perl inside character classes. The character was understood literally.
<P></P>
<DT><STRONG><A NAME="item_%2F%25s%2F_should_probably_be_written_as_%22%25s%2">/%s/ should probably be written as ``%s''</A></STRONG><BR>
<DD>
(W syntax) You have used a pattern where Perl expected to find a string,
as in the first argument to <A HREF="../../lib/Pod/perlfunc.html#item_join"><CODE>join</CODE></A>. Perl will treat the true
or false result of matching the pattern against $_ as the string,
which is probably not what you had in mind.
<P></P>
<DT><STRONG><A NAME="item_s">%s() called too early to check prototype</A></STRONG><BR>
<DD>
(W prototype) You've called a function that has a prototype before the parser saw a
definition or declaration for it, and Perl could not check that the call
conforms to the prototype. You need to either add an early prototype
declaration for the subroutine in question, or move the subroutine
definition ahead of the call to get proper prototype checking. Alternatively,
if you are certain that you're calling the function correctly, you may put
an ampersand before the name to avoid the warning. See <A HREF="../../lib/Pod/perlsub.html">the perlsub manpage</A>.
<P></P>
<DT><STRONG><A NAME="item_%s">%s argument is not a HASH or ARRAY element</A></STRONG><BR>
<DD>
(F) The argument to <A HREF="../../lib/Pod/perlfunc.html#item_exists"><CODE>exists()</CODE></A> must be a hash or array element, such as:
<PRE>
$foo{$bar}
$ref->{"susie"}[12]</PRE>
<P></P>
<DT><STRONG>%s argument is not a HASH or ARRAY element or slice</STRONG><BR>
<DD>
(F) The argument to <A HREF="#item_delete"><CODE>delete()</CODE></A> must be either a hash or array element, such as:
<PRE>
$foo{$bar}
$ref->{"susie"}[12]</PRE>
<P>or a hash or array slice, such as:</P>
<PRE>
@foo[$bar, $baz, $xyzzy]
@{$ref->[12]}{"susie", "queue"}</PRE>
<P></P>
<DT><STRONG>%s argument is not a subroutine name</STRONG><BR>
<DD>
(F) The argument to <A HREF="../../lib/Pod/perlfunc.html#item_exists"><CODE>exists()</CODE></A> for <CODE>exists &sub</CODE> must be a subroutine
name, and not a subroutine call. <A HREF="../../lib/Pod/perlfunc.html#item_sub"><CODE>exists &sub()</CODE></A> will generate this error.
<P></P>
<DT><STRONG>%s package attribute may clash with future reserved word: %s</STRONG><BR>
<DD>
(W reserved) A lowercase attribute name was used that had a package-specific handler.
That name might have a meaning to Perl itself some day, even though it
doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
See <A HREF="../../lib/attributes.html">the attributes manpage</A>.
(S) You requested an inplace edit without creating a backup file. Perl
was unable to remove the original file to replace it with the modified
file. The file was left unmodified.
<P></P>
<DT><STRONG><A NAME="item_Can%27t_return_%25s_from_lvalue_subroutine">Can't return %s from lvalue subroutine</A></STRONG><BR>
<DD>
(F) Perl detected an attempt to return illegal lvalues (such
as temporary or readonly values) from a subroutine used as an lvalue.
This is not allowed.
<P></P>
<DT><STRONG><A NAME="item_Can%27t_weaken_a_nonreference">Can't weaken a nonreference</A></STRONG><BR>
<DD>
(F) You attempted to weaken something that was not a reference. Only
references can be weakened.
<P></P>
<DT><STRONG><A NAME="item_Character_class_%5B%3A%25s%3A%5D_unknown">Character class [:%s:] unknown</A></STRONG><BR>
<DD>
(F) The class in the character class [: :] syntax is unknown.
See <A HREF="../../lib/Pod/perlre.html">the perlre manpage</A>.
<P></P>
<DT><STRONG><A NAME="item_Character_class_syntax_%5B%25s%5D_belongs_inside_c">Character class syntax [%s] belongs inside character classes</A></STRONG><BR>
<DD>
(W unsafe) The character class constructs [: :], [= =], and [. .] go
<EM>inside</EM> character classes, the [] are part of the construct,
for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
are not currently implemented; they are simply placeholders for
future extensions.
<P></P>
<DT><STRONG><A NAME="item_Constant_is_not_%25s_reference">Constant is not %s reference</A></STRONG><BR>
<DD>
(F) A constant value (perhaps declared using the <CODE>use constant</CODE> pragma)
is being dereferenced, but it amounts to the wrong type of reference. The
message indicates the type of reference that was expected. This usually
indicates a syntax error in dereferencing the constant value.
See <A HREF="../../lib/Pod/perlsub.html#constant functions">Constant Functions in the perlsub manpage</A> and <A HREF="../../lib/constant.html">the constant manpage</A>.
<P></P>
<DT><STRONG>constant(%s): %s</STRONG><BR>
<DD>
(F) The parser found inconsistencies either while attempting to define an
overloaded constant, or when trying to find the character name specified
in the <CODE>\N{...}</CODE> escape. Perhaps you forgot to load the corresponding
<CODE>overload</CODE> or <A HREF="#item_charnames"><CODE>charnames</CODE></A> pragma? See <A HREF="../../lib/charnames.html">the charnames manpage</A> and <A HREF="../../lib/overload.html">the overload manpage</A>.
<P></P>
<DT><STRONG><A NAME="item_CORE%3A%3A%25s_is_not_a_keyword">CORE::%s is not a keyword</A></STRONG><BR>
<DD>
(F) The CORE:: namespace is reserved for Perl keywords.
<P></P>
<DT><STRONG><A NAME="item_defined"><CODE>defined(@array)</CODE> is deprecated</A></STRONG><BR>
<DD>
(D) <A HREF="#item_defined"><CODE>defined()</CODE></A> is not usually useful on arrays because it checks for an
undefined <EM>scalar</EM> value. If you want to see if the array is empty,
just use <CODE>if (@array) { # not empty }</CODE> for example.
<P></P>
<DT><STRONG><CODE>defined(%hash)</CODE> is deprecated</STRONG><BR>
<DD>
(D) <A HREF="#item_defined"><CODE>defined()</CODE></A> is not usually useful on hashes because it checks for an
undefined <EM>scalar</EM> value. If you want to see if the hash is empty,
just use <CODE>if (%hash) { # not empty }</CODE> for example.
<P></P>
<DT><STRONG><A NAME="item_Did_not_produce_a_valid_header">Did not produce a valid header</A></STRONG><BR>
<DD>
See Server error.
<P></P>
<DT><STRONG><A NAME="item_%28Did_you_mean_%22local%22_instead_of_%22our%22%3">(Did you mean ``local'' instead of ``our''?)</A></STRONG><BR>
<DD>
(W misc) Remember that ``our'' does not localize the declared global variable.
You have declared it again in the same lexical scope, which seems superfluous.
<P></P>
<DT><STRONG><A NAME="item_Document_contains_no_data">Document contains no data</A></STRONG><BR>
(W digit) You may have tried to use a digit other than 0 or 1 in a binary number.
Interpretation of the binary number stopped before the offending digit.
<P></P>
<DT><STRONG><A NAME="item_Illegal_number_of_bits_in_vec">Illegal number of bits in vec</A></STRONG><BR>
<DD>
(F) The number of bits in <A HREF="#item_vec"><CODE>vec()</CODE></A> (the third argument) must be a power of
two from 1 to 32 (or 64, if your platform supports that).
<P></P>
<DT><STRONG><A NAME="item_Integer_overflow_in_%25s_number">Integer overflow in %s number</A></STRONG><BR>
<DD>
(W overflow) The hexadecimal, octal or binary number you have specified either
as a literal or as an argument to <A HREF="../../lib/Pod/perlfunc.html#item_hex"><CODE>hex()</CODE></A> or <A HREF="../../lib/Pod/perlfunc.html#item_oct"><CODE>oct()</CODE></A> is too big for your
architecture, and has been converted to a floating point number. On a
32-bit architecture the largest hexadecimal, octal or binary number
representable without overflow is 0xFFFFFFFF, 037777777777, or
0b11111111111111111111111111111111 respectively. Note that Perl
transparently promotes all numbers to a floating point representation
internally--subject to loss of precision errors in subsequent
The indicated attributes for a subroutine or variable were not recognized
by Perl or by a user-supplied handler. See <A HREF="../../lib/attributes.html">the attributes manpage</A>.
<P></P>
<DT><STRONG><A NAME="item_invalid_%5B%5D_range_%22%25s%22_in_regexp">invalid [] range ``%s'' in regexp</A></STRONG><BR>
<DD>
The offending range is now explicitly displayed.
<P></P>
<DT><STRONG><A NAME="item_Invalid_separator_character_%25s_in_attribute_list">Invalid separator character %s in attribute list</A></STRONG><BR>
<DD>
(F) Something other than a colon or whitespace was seen between the
elements of an attribute list. If the previous attribute
had a parenthesised parameter list, perhaps that list was terminated
too soon. See <A HREF="../../lib/attributes.html">the attributes manpage</A>.
<P></P>
<DT><STRONG><A NAME="item_Invalid_separator_character_%25s_in_subroutine_att">Invalid separator character %s in subroutine attribute list</A></STRONG><BR>
<DD>
(F) Something other than a colon or whitespace was seen between the
elements of a subroutine attribute list. If the previous attribute
had a parenthesised parameter list, perhaps that list was terminated
(W y2k) You are concatenating the number 19 with another number, which
could be a potential Year 2000 problem.
<P></P>
<DT><STRONG><A NAME="item_pragma_%22attrs%22_is_deprecated%2C_use_%22sub_NAM">pragma ``attrs'' is deprecated, use ``sub NAME : ATTRS'' instead</A></STRONG><BR>
<DD>
(W deprecated) You have written somehing like this:
<PRE>
sub doit
{
use attrs qw(locked);
}</PRE>
<P>You should use the new declaration syntax instead.</P>
<PRE>
sub doit : locked
{
...</PRE>
<P>The <CODE>use attrs</CODE> pragma is now obsolete, and is only provided for
backward-compatibility. See <A HREF="../../lib/Pod/perlsub.html#subroutine attributes">Subroutine Attributes in the perlsub manpage</A>.</P>
<P></P>
<DT><STRONG><A NAME="item_Premature_end_of_script_headers">Premature end of script headers</A></STRONG><BR>
<DD>
See Server error.
<P></P>
<DT><STRONG><A NAME="item_Repeat_count_in_pack_overflows">Repeat count in pack overflows</A></STRONG><BR>
<DD>
(F) You can't specify a repeat count so large that it overflows
your signed integers. See <A HREF="../../lib/Pod/perlfunc.html#pack">pack in the perlfunc manpage</A>.
<P></P>
<DT><STRONG><A NAME="item_Repeat_count_in_unpack_overflows">Repeat count in unpack overflows</A></STRONG><BR>
<DD>
(F) You can't specify a repeat count so large that it overflows
your signed integers. See <A HREF="../../lib/Pod/perlfunc.html#unpack">unpack in the perlfunc manpage</A>.
<P></P>
<DT><STRONG><CODE>realloc()</CODE> of freed memory ignored</STRONG><BR>
<DD>
(S) An internal routine called <A HREF="#item_realloc"><CODE>realloc()</CODE></A> on something that had already
been freed.
<P></P>
<DT><STRONG><A NAME="item_Reference_is_already_weak">Reference is already weak</A></STRONG><BR>
<DD>
(W misc) You have attempted to weaken a reference that is already weak.
Doing so has no effect.
<P></P>
<DT><STRONG><A NAME="item_setpgrp_can%27t_take_arguments">setpgrp can't take arguments</A></STRONG><BR>
<DD>
(F) Your system has the <A HREF="../../lib/Pod/perlfunc.html#item_setpgrp"><CODE>setpgrp()</CODE></A> from BSD 4.2, which takes no arguments,
unlike POSIX setpgid(), which takes a process ID and process group ID.
<P></P>
<DT><STRONG><A NAME="item_Strange_%2A%2B%3F%7B%7D_on_zero%2Dlength_expressio">Strange *+?{} on zero-length expression</A></STRONG><BR>
<DD>
(W regexp) You applied a regular expression quantifier in a place where it
makes no sense, such as on a zero-width assertion.
Try putting the quantifier inside the assertion instead. For example,
the way to match ``abc'' provided that it is followed by three
repetitions of ``xyz'' is <CODE>/abc(?=(?:xyz){3})/</CODE>, not <CODE>/abc(?=xyz){3}/</CODE>.
<P></P>
<DT><STRONG><A NAME="item_switching_effective_%25s_is_not_implemented">switching effective %s is not implemented</A></STRONG><BR>
<DD>
(F) While under the <CODE>use filetest</CODE> pragma, we cannot switch the
real and effective uids or gids.
<P></P>
<DT><STRONG><A NAME="item_elements">This Perl can't reset CRTL environ elements (%s)</A></STRONG><BR>
<DD>
<DT><STRONG>This Perl can't set CRTL environ elements (%s=%s)</STRONG><BR>
<DD>
(W internal) Warnings peculiar to VMS. You tried to change or delete an element
of the CRTL's internal environ array, but your copy of Perl wasn't
built with a CRTL that contained the <CODE>setenv()</CODE> function. You'll need to
rebuild Perl with a CRTL that does, or redefine <EM>PERL_ENV_TABLES</EM> (see
<A HREF="../../lib/Pod/perlvms.html">the perlvms manpage</A>) so that the environ array isn't the target of the change to
%ENV which produced the warning.
<P></P>
<DT><STRONG><A NAME="item_Too_late_to_run_%25s_block">Too late to run %s block</A></STRONG><BR>
<DD>
(W void) A CHECK or INIT block is being defined during run time proper,
when the opportunity to run them has already passed. Perhaps you are
loading a file with <A HREF="../../lib/Pod/perlfunc.html#item_require"><CODE>require</CODE></A> or <A HREF="../../lib/Pod/perlfunc.html#item_do"><CODE>do</CODE></A> when you should be using
<A HREF="../../lib/Pod/perlfunc.html#item_use"><CODE>use</CODE></A> instead. Or perhaps you should put the <A HREF="../../lib/Pod/perlfunc.html#item_require"><CODE>require</CODE></A> or <A HREF="../../lib/Pod/perlfunc.html#item_do"><CODE>do</CODE></A>
<P>Beware that any new warnings that have been added or old ones
that have been enhanced are <STRONG>not</STRONG> considered incompatible changes.</P>
<P>Since all new warnings must be explicitly requested via the <CODE>-w</CODE>
switch or the <CODE>warnings</CODE> pragma, it is ultimately the programmer's
responsibility to ensure that warnings are enabled judiciously.</P>
<DL>
<DT><STRONG><A NAME="item_CHECK_is_a_new_keyword">CHECK is a new keyword</A></STRONG><BR>
<DD>
All subroutine definitions named CHECK are now special. See
<CODE>/"Support for CHECK blocks"</CODE> for more information.
<P></P>
<DT><STRONG><A NAME="item_Treatment_of_list_slices_of_undef_has_changed">Treatment of list slices of undef has changed</A></STRONG><BR>
<DD>
There is a potential incompatibility in the behavior of list slices
that are comprised entirely of undefined values.
See <A HREF="#behavior of list slices is more consistent">Behavior of list slices is more consistent</A>.
<P></P></DL>
<P>
<H2><A NAME="format of $english::perl_version is different">Format of $English::PERL_VERSION is different</A></H2>
<P>The English module now sets $PERL_VERSION to $^V (a string value) rather
than <CODE>$]</CODE> (a numeric value). This is a potential incompatibility.
Send us a report via perlbug if you are affected by this.</P>
<P>See <A HREF="#improved perl version numbering system">Improved Perl version numbering system</A> for the reasons for
this change.</P>
<DL>
<DT><STRONG><A NAME="item_Literals_of_the_form_1%2E2%2E3_parse_differently">Literals of the form <CODE>1.2.3</CODE> parse differently</A></STRONG><BR>
<DD>
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.
<P>For example, <CODE>print 97.98.99</CODE> used to output <CODE>97.9899</CODE> in earlier
versions, but now prints <CODE>abc</CODE>.</P>
<P>See <A HREF="#support for strings represented as a vector of ordinals">Support for strings represented as a vector of ordinals</A>.</P>
<P></P>
<DT><STRONG><A NAME="item_Possibly_changed_pseudo%2Drandom_number_generator">Possibly changed pseudo-random number generator</A></STRONG><BR>
<DD>
Perl programs that depend on reproducing a specific set of pseudo-random
numbers may now produce different output due to improvements made to the
<A HREF="../../lib/Pod/perlfunc.html#item_rand"><CODE>rand()</CODE></A> builtin. You can use <CODE>sh Configure -Drandfunc=rand</CODE> to obtain
the old behavior.
<P>See <A HREF="#better pseudorandom number generator">Better pseudo-random number generator</A>.</P>
<P></P>
<DT><STRONG><A NAME="item_Hashing_function_for_hash_keys_has_changed">Hashing function for hash keys has changed</A></STRONG><BR>
<DD>
Even though Perl hashes are not order preserving, the apparently
random order encountered when iterating on the contents of a hash
is actually determined by the hashing algorithm used. Improvements
in the algorithm may yield a random order that is <STRONG>different</STRONG> from
that of previous versions, especially when iterating on hashes.
<P>See <A HREF="#better worstcase behavior of hashes">Better worst-case behavior of hashes</A> for additional
information.</P>
<P></P>
<DT><STRONG><A NAME="item_undef_fails_on_read_only_values"><A HREF="../../lib/Pod/perlfunc.html#item_undef"><CODE>undef</CODE></A> fails on read only values</A></STRONG><BR>
<DD>
Using the <A HREF="../../lib/Pod/perlfunc.html#item_undef"><CODE>undef</CODE></A> operator on a readonly value (such as $1) has
the same effect as assigning <A HREF="../../lib/Pod/perlfunc.html#item_undef"><CODE>undef</CODE></A> to the readonly value--it
throws an exception.
<P></P>
<DT><STRONG><A NAME="item_Close%2Don%2Dexec_bit_may_be_set_on_pipe_and_socke">Close-on-exec bit may be set on pipe and socket handles</A></STRONG><BR>
<DD>
Pipe and socket handles are also now subject to the close-on-exec
<DT><STRONG><A NAME="item_Writing_%22%24%241%22_to_mean_%22%24%7B%24%7D1%22_">Writing <CODE>"$$1"</CODE> to mean <CODE>"${$}1"</CODE> is unsupported</A></STRONG><BR>
<DD>
Perl 5.004 deprecated the interpretation of <CODE>$$1</CODE> and
similar within interpolated strings to mean <CODE>$$ . "1"</CODE>,
but still allowed it.
<P>In Perl 5.6.0 and later, <CODE>"$$1"</CODE> always means <CODE>"${$1}"</CODE>.</P>
<P></P>
<DT><STRONG>delete(), <A HREF="../../lib/Pod/perlfunc.html#item_values"><CODE>values()</CODE></A> and <CODE>\(%h)</CODE> operate on aliases to values, not copies</STRONG><BR>
<DD>
delete(), each(), <A HREF="../../lib/Pod/perlfunc.html#item_values"><CODE>values()</CODE></A> and hashes in a list context return the actual
values in the hash, instead of copies (as they used to in earlier
versions). Typical idioms for using these constructs copy the
returned values, but this can make a significant difference when
creating references to the returned values. Keys in the hash are still
returned as copies when iterating on a hash.
<P>See also <A HREF="#delete(), each(), values() and hash iteration are faster">delete(), each(), values() and hash iteration are faster</A>.</P>
<A HREF="#item_vec"><CODE>vec()</CODE></A> generates a run-time error if the BITS argument is not
a valid power-of-two integer.
<P></P>
<DT><STRONG><A NAME="item_Text_of_some_diagnostic_output_has_changed">Text of some diagnostic output has changed</A></STRONG><BR>
<DD>
Most references to internal Perl operations in diagnostics
have been changed to be more descriptive. This may be an
issue for programs that may incorrectly rely on the exact
text of diagnostics for proper functioning.
<P></P>
<DT><STRONG><A NAME="item_%@"><CODE>%@</CODE> has been removed</A></STRONG><BR>
<DD>
The undocumented special variable <A HREF="#item_%@"><CODE>%@</CODE></A> that used to accumulate
``background'' errors (such as those that happen in <CODE>DESTROY())</CODE>
has been removed, because it could potentially result in memory
leaks.
<P></P>
<DT><STRONG><A NAME="item_not">Parenthesized <CODE>not()</CODE> behaves like a list operator</A></STRONG><BR>
<DD>
The <A HREF="#item_not"><CODE>not</CODE></A> operator now falls under the ``if it looks like a function,
it behaves like a function'' rule.
<P>As a result, the parenthesized form can be used with <A HREF="../../lib/Pod/perlfunc.html#item_grep"><CODE>grep</CODE></A> and <A HREF="../../lib/Pod/perlfunc.html#item_map"><CODE>map</CODE></A>.
The following construct used to be a syntax error before, but it works
as expected now:</P>
<PRE>
grep not($_), @things;</PRE>
<P>On the other hand, using <A HREF="#item_not"><CODE>not</CODE></A> with a literal list slice may not
work. The following previously allowed construct:</P>
<PRE>
print not (1,2,3)[0];</PRE>
<P>needs to be written with additional parentheses now:</P>
<PRE>
print not((1,2,3)[0]);</PRE>
<P>The behavior remains unaffected when <A HREF="#item_not"><CODE>not</CODE></A> is not followed by parentheses.</P>
<P></P>
<DT><STRONG>Semantics of bareword prototype <CODE>(*)</CODE> have changed</STRONG><BR>
<DD>
The semantics of the bareword prototype <CODE>*</CODE> have changed. Perl 5.005
always coerced simple scalar arguments to a typeglob, which wasn't useful
in situations where the subroutine must distinguish between a simple
scalar and a typeglob. The new behavior is to not coerce bareword
arguments to a typeglob. The value will always be visible as either
<H2><A NAME="thread test failures">Thread test failures</A></H2>
<P>The subtests 19 and 20 of lib/thr5005.t test are known to fail due to
fundamental problems in the 5.005 threading implementation. These are
not new failures--Perl 5.005_0x has the same bugs, but didn't have these
tests.</P>
<P>
<H2><A NAME="ebcdic platforms not supported">EBCDIC platforms not supported</A></H2>
<P>In earlier releases of Perl, EBCDIC environments like OS390 (also
known as Open Edition MVS) and VM-ESA were supported. Due to changes
required by the UTF-8 (Unicode) support, the EBCDIC platforms are not
supported in Perl 5.6.0.</P>
<P>
<H2><A NAME="in 64bit hpux the lib/io_multihomed test may hang">In 64-bit HP-UX the lib/io_multihomed test may hang</A></H2>
<P>The lib/io_multihomed test may hang in HP-UX if Perl has been
configured to be 64-bit. Because other 64-bit platforms do not
hang in this test, HP-UX is suspect. All other tests pass
in 64-bit HP-UX. The test attempts to create and connect to
``multihomed'' sockets (sockets which have multiple IP addresses).</P>
<P>
<H2><A NAME="nextstep 3.3 posix test failure">NEXTSTEP 3.3 POSIX test failure</A></H2>
<P>In NEXTSTEP 3.3p2 the implementation of the <CODE>strftime(3)</CODE> in the
operating system libraries is buggy: the %j format numbers the days of
a month starting from zero, which, while being logical to programmers,
will cause the subtests 19 to 27 of the lib/posix test may fail.</P>
<P>
<H2><A NAME="tru64 (aka digital unix, aka dec osf/1) lib/sdbm test failure with gcc">Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with gcc</A></H2>
<P>If compiled with gcc 2.95 the lib/sdbm test will fail (dump core).
The cure is to use the vendor cc, it comes with the operating system
and produces good code.</P>
<P>
<H2><A NAME="unicos/mk cc failures during configure run">UNICOS/mk CC failures during Configure run</A></H2>
<P>In UNICOS/mk the following errors may appear during the Configure run:</P>
<PRE>
Guessing which symbols your C compiler and preprocessor define...
<DT><STRONG><A NAME="item_Character_class_syntax_%5B%3A_%3A%5D_is_reserved_f">Character class syntax [: :] is reserved for future extensions</A></STRONG><BR>
<DD>
(W) Within regular expression character classes ([]) the syntax beginning
with ``[:'' and ending with ``:]'' is reserved for future extensions.
If you need to represent those character sequences inside a regular
expression character class, just quote the square brackets with the
backslash: ``\[:'' and ``:\]''.
<P></P>
<DT><STRONG><A NAME="item_Ill%2Dformed_logical_name_%7C%25s%7C_in_prime_env_">Ill-formed logical name |%s| in prime_env_iter</A></STRONG><BR>
<DD>
(W) A warning peculiar to VMS. A logical name was encountered when preparing
to iterate over %ENV which violates the syntactic rules governing logical
names. Because it cannot be translated normally, it is skipped, and will not
appear in %ENV. This may be a benign occurrence, as some software packages
might directly modify logical name tables and introduce nonstandard names,
or it may indicate that a logical name table has been corrupted.
<P></P>
<DT><STRONG><A NAME="item_Probable_precedence_problem_on_%25s">Probable precedence problem on %s</A></STRONG><BR>
<DD>
(W) The compiler found a bareword where it expected a conditional,
which often indicates that an || or && was parsed as part of the
last argument of the previous construct, for example:
<PRE>
open FOO || die;</PRE>
<P></P>
<DT><STRONG><A NAME="item_regexp_too_big">regexp too big</A></STRONG><BR>
<DD>
(F) The current implementation of regular expressions uses shorts as
address offsets within a string. Unfortunately this means that if
the regular expression compiles to longer than 32767, it'll blow up.
Usually when you want a regular expression this big, there is a better
way to do it with multiple statements. See <A HREF="../../lib/Pod/perlre.html">the perlre manpage</A>.
<P></P>
<DT><STRONG><A NAME="item_Use_of_%22%24%24%3Cdigit%3E%22_to_mean_%22%24%7B%2">Use of ``$$<digit>'' to mean ``${$}<digit>'' is deprecated</A></STRONG><BR>
<DD>
(D) Perl versions before 5.004 misinterpreted any type marker followed
by ``$'' and a digit. For example, ``$$0'' was incorrectly taken to mean
``${$}0'' instead of ``${$0}''. This bug is (mostly) fixed in Perl 5.004.
<P>However, the developers of Perl 5.004 could not fix this bug completely,
because at least two widely-used modules depend on the old meaning of
``$$0'' in a string. So Perl 5.004 still interprets ``$$<digit>'' in the
old (broken) way inside strings; but it generates this message as a
warning. And in Perl 5.005, this special treatment will cease.</P>
