PERL561DELTA(1) Perl Programmers Reference Guide PERL561DELTA(1)NAMEperl561delta - what's new for perl v5.6.x
DESCRIPTION
This document describes differences between the 5.005
release and the 5.6.1 release.
Summary of changes between 5.6.0 and 5.6.1
This section contains a summary of the changes between the
5.6.0 release and the 5.6.1 release. More details about the
changes mentioned here may be found in the Changes files
that accompany the Perl source distribution. See perlhack
for pointers to online resources where you can inspect the
individual patches described by these changes.
Security Issues
suidperl will not run /bin/mail anymore, because some plat-
forms have a /bin/mail that is vulnerable to buffer overflow
attacks.
Note that suidperl is neither built nor installed by default
in any recent version of perl. Use of suidperl is highly
discouraged. If you think you need it, try alternatives such
as sudo first. See http://www.courtesan.com/sudo/ .
Core bug fixes
This is not an exhaustive list. It is intended to cover
only the significant user-visible changes.
"UNIVERSAL::isa()"
A bug in the caching mechanism used by
"UNIVERSAL::isa()" that affected base.pm has been fixed.
The bug has existed since the 5.005 releases, but wasn't
tickled by base.pm in those releases.
Memory leaks
Various cases of memory leaks and attempts to access
uninitialized memory have been cured. See "Known Prob-
lems" below for further issues.
Numeric conversions
Numeric conversions did not recognize changes in the
string value properly in certain circumstances.
In other situations, large unsigned numbers (those above
2**31) could sometimes lose their unsignedness, causing
bogus results in arithmetic operations.
Integer modulus on large unsigned integers sometimes
returned incorrect values.
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Perl 5.6.0 generated "not a number" warnings on certain
conversions where previous versions didn't.
These problems have all been rectified.
Infinity is now recognized as a number.
qw(a\\b)
In Perl 5.6.0, qw(a\\b) produced a string with two
backslashes instead of one, in a departure from the
behavior in previous versions. The older behavior has
been reinstated.
caller()caller() could cause core dumps in certain situations.
Carp was sometimes affected by this problem.
Bugs in regular expressions
Pattern matches on overloaded values are now handled
correctly.
Perl 5.6.0 parsed m/\x{ab}/ incorrectly, leading to
spurious warnings. This has been corrected.
The RE engine found in Perl 5.6.0 accidentally pessim-
ised certain kinds of simple pattern matches. These are
now handled better.
Regular expression debug output (whether through "use re
'debug'" or via "-Dr") now looks better.
Multi-line matches like ""a\nxb\n" =~ /(?!\A)x/m" were
flawed. The bug has been fixed.
Use of $& could trigger a core dump under some situa-
tions. This is now avoided.
Match variables $1 et al., weren't being unset when a
pattern match was backtracking, and the anomaly showed
up inside "/...(?{ ... }).../" etc. These variables are
now tracked correctly.
pos() did not return the correct value within s///ge in
earlier versions. This is now handled correctly.
"slurp" mode
readline() on files opened in "slurp" mode could return
an extra "" at the end in certain situations. This has
been corrected.
Autovivification of symbolic references to special variables
Autovivification of symbolic references of special
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variables described in perlvar (as in "${$num}") was
accidentally disabled. This works again now.
Lexical warnings
Lexical warnings now propagate correctly into "eval
"..."".
"use warnings qw(FATAL all)" did not work as intended.
This has been corrected.
Lexical warnings could leak into other scopes in some
situations. This is now fixed.
warnings::enabled() now reports the state of $^W
correctly if the caller isn't using lexical warnings.
Spurious warnings and errors
Perl 5.6.0 could emit spurious warnings about redefini-
tion of dl_error() when statically building extensions
into perl. This has been corrected.
"our" variables could result in bogus "Variable will not
stay shared" warnings. This is now fixed.
"our" variables of the same name declared in two sibling
blocks resulted in bogus warnings about "redeclaration"
of the variables. The problem has been corrected.
glob()
Compatibility of the builtin glob() with old csh-based
glob has been improved with the addition of
GLOB_ALPHASORT option. See "File::Glob".
File::Glob::glob() has been renamed to
File::Glob::bsd_glob() because the name clashes with the
builtin glob(). The older name is still available for
compatibility, but is deprecated.
Spurious syntax errors generated in certain situations,
when glob() caused File::Glob to be loaded for the first
time, have been fixed.
Tainting
Some cases of inconsistent taint propagation (such as
within hash values) have been fixed.
The tainting behavior of sprintf() has been rational-
ized. It does not taint the result of floating point
formats anymore, making the behavior consistent with
that of string interpolation.
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Arguments to sort() weren't being provided the right
wantarray() context. The comparison block is now run in
scalar context, and the arguments to be sorted are
always provided list context.
sort() is also fully reentrant, in the sense that the
sort function can itself call sort(). This did not work
reliably in previous releases.
#line directives
#line directives now work correctly when they appear at
the very beginning of "eval "..."".
Subroutine prototypes
The (\&) prototype now works properly.
map()map() could get pathologically slow when the result list
it generates is larger than the source list. The per-
formance has been improved for common scenarios.
Debugger
Debugger exit code now reflects the script exit code.
Condition "0" in breakpoints is now treated correctly.
The "d" command now checks the line number.
$. is no longer corrupted by the debugger.
All debugger output now correctly goes to the socket if
RemotePort is set.
PERL5OPT
PERL5OPT can be set to more than one switch group. Pre-
viously, it used to be limited to one group of options
only.
chop()
chop(@list) in list context returned the characters
chopped in reverse order. This has been reversed to be
in the right order.
Unicode support
Unicode support has seen a large number of incremental
improvements, but continues to be highly experimental.
It is not expected to be fully supported in the 5.6.x
maintenance releases.
substr(), join(), repeat(), reverse(), quotemeta() and
string concatenation were all handling Unicode strings
incorrectly in Perl 5.6.0. This has been corrected.
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Support for "tr///CU" and "tr///UC" etc., have been
removed since we realized the interface is broken. For
similar functionality, see "pack" in perlfunc.
The Unicode Character Database has been updated to ver-
sion 3.0.1 with additions made available to the public
as of August 30, 2000.
The Unicode character classes \p{Blank} and
\p{SpacePerl} have been added. "Blank" is like C
isblank(), that is, it contains only "horizontal whi-
tespace" (the space character is, the newline isn't),
and the "SpacePerl" is the Unicode equivalent of "\s"
(\p{Space} isn't, since that includes the vertical tabu-
lator character, whereas "\s" doesn't.)
If you are experimenting with Unicode support in perl,
the development versions of Perl may have more to offer.
In particular, I/O layers are now available in the
development track, but not in the maintenance track,
primarily to do backward compatibility issues. Unicode
support is also evolving rapidly on a daily basis in the
development track--the maintenance track only reflects
the most conservative of these changes.
64-bit support
Support for 64-bit platforms has been improved, but con-
tinues to be experimental. The level of support varies
greatly among platforms.
Compiler
The B Compiler and its various backends have had many
incremental improvements, but they continue to remain
highly experimental. Use in production environments is
discouraged.
The perlcc tool has been rewritten so that the user
interface is much more like that of a C compiler.
The perlbc tools has been removed. Use "perlcc -B"
instead.
Lvalue subroutines
There have been various bugfixes to support lvalue sub-
routines better. However, the feature still remains
experimental.
IO::Socket
IO::Socket::INET failed to open the specified port if
the service name was not known. It now correctly uses
the supplied port number as is.
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File::Find
File::Find now chdir()s correctly when chasing symbolic
links.
xsubpp
xsubpp now tolerates embedded POD sections.
"no Module;"
"no Module;" does not produce an error even if Module
does not have an unimport() method. This parallels the
behavior of "use" vis-a-vis "import".
Tests
A large number of tests have been added.
Core features
untie() will now call an UNTIE() hook if it exists. See
perltie for details.
The "-DT" command line switch outputs copious tokenizing
information. See perlrun.
Arrays are now always interpolated in double-quotish
strings. Previously, "foo@bar.com" used to be a fatal error
at compile time, if an array @bar was not used or declared.
This transitional behavior was intended to help migrate
perl4 code, and is deemed to be no longer useful. See
"Arrays now always interpolate into double-quoted strings".
keys(), each(), pop(), push(), shift(), splice() and
unshift() can all be overridden now.
"my __PACKAGE__ $obj" now does the expected thing.
Configuration issues
On some systems (IRIX and Solaris among them) the system
malloc is demonstrably better. While the defaults haven't
been changed in order to retain binary compatibility with
earlier releases, you may be better off building perl with
"Configure -Uusemymalloc ..." as discussed in the INSTALL
file.
"Configure" has been enhanced in various ways:
+ Minimizes use of temporary files.
+ By default, does not link perl with libraries not used
by it, such as the various dbm libraries. SunOS 4.x
hints preserve behavior on that platform.
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+ Support for pdp11-style memory models has been removed
due to obsolescence.
+ Building outside the source tree is supported on systems
that have symbolic links. This is done by running
sh /path/to/source/Configure -Dmksymlinks ...
make all test install
in a directory other than the perl source directory.
See INSTALL.
+ "Configure -S" can be run non-interactively.
Documentation
README.aix, README.solaris and README.macos have been added.
README.posix-bc has been renamed to README.bs2000. These
are installed as perlaix, perlsolaris, perlmacos, and
perlbs2000 respectively.
The following pod documents are brand new:
perlclib Internal replacements for standard C library functions
perldebtut Perl debugging tutorial
perlebcdic Considerations for running Perl on EBCDIC platforms
perlnewmod Perl modules: preparing a new module for distribution
perlrequick Perl regular expressions quick start
perlretut Perl regular expressions tutorial
perlutil utilities packaged with the Perl distribution
The INSTALL file has been expanded to cover various issues,
such as 64-bit support.
A longer list of contributors has been added to the source
distribution. See the file "AUTHORS".
Numerous other changes have been made to the included docu-
mentation and FAQs.
Bundled modules
The following modules have been added.
B::Concise
Walks Perl syntax tree, printing concise info about ops.
See B::Concise.
File::Temp
Returns name and handle of a temporary file safely. See
File::Temp.
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Pod::LaTeX
Converts Pod data to formatted LaTeX. See Pod::LaTeX.
Pod::Text::Overstrike
Converts POD data to formatted overstrike text. See
Pod::Text::Overstrike.
The following modules have been upgraded.
CGI CGI v2.752 is now included.
CPAN
CPAN v1.59_54 is now included.
Class::Struct
Various bugfixes have been added.
DB_File
DB_File v1.75 supports newer Berkeley DB versions, among
other improvements.
Devel::Peek
Devel::Peek has been enhanced to support dumping of
memory statistics, when perl is built with the included
malloc().
File::Find
File::Find now supports pre and post-processing of the
files in order to sort() them, etc.
Getopt::Long
Getopt::Long v2.25 is included.
IO::Poll
Various bug fixes have been included.
IPC::Open3
IPC::Open3 allows use of numeric file descriptors.
Math::BigFloat
The fmod() function supports modulus operations. Vari-
ous bug fixes have also been included.
Math::Complex
Math::Complex handles inf, NaN etc., better.
Net::Ping
ping() could fail on odd number of data bytes, and when
the echo service isn't running. This has been
corrected.
Opcode
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A memory leak has been fixed.
Pod::Parser
Version 1.13 of the Pod::Parser suite is included.
Pod::Text
Pod::Text and related modules have been upgraded to the
versions in podlators suite v2.08.
SDBM_File
On dosish platforms, some keys went missing because of
lack of support for files with "holes". A workaround
for the problem has been added.
Sys::Syslog
Various bug fixes have been included.
Tie::RefHash
Now supports Tie::RefHash::Nestable to automagically tie
hashref values.
Tie::SubstrHash
Various bug fixes have been included.
Platform-specific improvements
The following new ports are now available.
NCR MP-RAS
NonStop-UX
Perl now builds under Amdahl UTS.
Perl has also been verified to build under Amiga OS.
Support for EPOC has been much improved. See README.epoc.
Building perl with -Duseithreads or -Duse5005threads now
works under HP-UX 10.20 (previously it only worked under
10.30 or later). You will need a thread library package
installed. See README.hpux.
Long doubles should now work under Linux.
Mac OS Classic is now supported in the mainstream source
package. See README.macos.
Support for MPE/iX has been updated. See README.mpeix.
Support for OS/2 has been improved. See "os2/Changes" and
README.os2.
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Dynamic loading on z/OS (formerly OS/390) has been improved.
See README.os390.
Support for VMS has seen many incremental improvements,
including better support for operators like backticks and
system(), and better %ENV handling. See "README.vms" and
perlvms.
Support for Stratus VOS has been improved. See
"vos/Changes" and README.vos.
Support for Windows has been improved.
+ fork() emulation has been improved in various ways, but
still continues to be experimental. See perlfork for
known bugs and caveats.
+ %SIG has been enabled under USE_ITHREADS, but its use is
completely unsupported under all configurations.
+ Borland C++ v5.5 is now a supported compiler that can
build Perl. However, the generated binaries continue to
be incompatible with those generated by the other sup-
ported compilers (GCC and Visual C++).
+ Non-blocking waits for child processes (or
pseudo-processes) are supported via "waitpid($pid,
&POSIX::WNOHANG)".
+ A memory leak in accept() has been fixed.
+ wait(), waitpid() and backticks now return the correct
exit status under Windows 9x.
+ Trailing new %ENV entries weren't propagated to child
processes. This is now fixed.
+ Current directory entries in %ENV are now correctly pro-
pagated to child processes.
+ Duping socket handles with open(F, ">&MYSOCK") now works
under Windows 9x.
+ The makefiles now provide a single switch to bulk-enable
all the features enabled in ActiveState ActivePerl (a
popular binary distribution).
+ Win32::GetCwd() correctly returns C:\ instead of C: when
at the drive root. Other bugs in chdir() and Cwd::cwd()
have also been fixed.
+ fork() correctly returns undef and sets EAGAIN when it
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runs out of pseudo-process handles.
+ ExtUtils::MakeMaker now uses $ENV{LIB} to search for
libraries.
+ UNC path handling is better when perl is built to sup-
port fork().
+ A handle leak in socket handling has been fixed.
+ send() works from within a pseudo-process.
Unless specifically qualified otherwise, the remainder of
this document covers changes between the 5.005 and 5.6.0
releases.
Core Enhancements
Interpreter cloning, threads, and concurrency
Perl 5.6.0 introduces the beginnings of support for running
multiple interpreters concurrently in different threads. In
conjunction with the perl_clone() API call, which can be
used to selectively duplicate the state of any given inter-
preter, it is possible to compile a piece of code once in an
interpreter, clone that interpreter one or more times, and
run all the resulting interpreters in distinct threads.
On the Windows platform, this feature is used to emulate
fork() at the interpreter level. See perlfork for details
about that.
This feature is still in evolution. It is eventually meant
to be used to selectively clone a subroutine and data reach-
able from that subroutine in a separate interpreter and run
the cloned subroutine in a separate thread. Since there is
no shared data between the interpreters, little or no lock-
ing will be needed (unless parts of the symbol table are
explicitly shared). This is obviously intended to be an
easy-to-use replacement for the existing threads support.
Support for cloning interpreters and interpreter concurrency
can be enabled using the -Dusethreads Configure option (see
win32/Makefile for how to enable it on Windows.) The
resulting perl executable will be functionally identical to
one that was built with -Dmultiplicity, but the perl_clone()
API call will only be available in the former.
-Dusethreads enables the cpp macro USE_ITHREADS by default,
which in turn enables Perl source code changes that provide
a clear separation between the op tree and the data it
operates with. The former is immutable, and can therefore
be shared between an interpreter and all of its clones,
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while the latter is considered local to each interpreter,
and is therefore copied for each clone.
Note that building Perl with the -Dusemultiplicity Configure
option is adequate if you wish to run multiple independent
interpreters concurrently in different threads.
-Dusethreads only provides the additional functionality of
the perl_clone() API call and other support for running
cloned interpreters concurrently.
NOTE: This is an experimental feature. Implementation details are
subject to change.
Lexically scoped warning categories
You can now control the granularity of warnings emitted by
perl at a finer level using the "use warnings" pragma.
warnings and perllexwarn have copious documentation on this
feature.
Unicode and UTF-8 support
Perl now uses UTF-8 as its internal representation for char-
acter strings. The "utf8" and "bytes" pragmas are used to
control this support in the current lexical scope. See per-
lunicode, utf8 and bytes for more information.
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 com-
plete the toolkit for dealing with Unicode.
NOTE: This should be considered an experimental feature. Implementation
details are subject to change.
Support for interpolating named characters
The new "\N" escape interpolates named characters within
strings. For example, "Hi! \N{WHITE SMILING FACE}" evaluates
to a string with a Unicode smiley face at the end.
"our" declarations
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 "vars" pragma, but also provides the opportunity to
introduce typing and other attributes for such variables.
See "our" in perlfunc.
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Support for strings represented as a vector of ordinals
Literals of the form "v1.2.3.4" 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
"\x{1}\x{2}\x{3}\x{4}". The leading "v" may be omitted if
there are more than two ordinals, so 1.2.3 is parsed the
same as "v1.2.3".
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 "eq", "ne", "lt",
"gt", etc., or perform bitwise string operations on them
using "|", "&", etc.
In conjunction with the new $^V magic variable (which con-
tains the perl version as a string), such literals can be
used as a readable way to check if you're running a particu-
lar version of Perl:
# this will parse in older versions of Perl also
if ($^V and $^V gt v5.6.0) {
# new features supported
}
"require" and "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
Alternatively, the "v" may be omitted if there is more than
one dot:
require 5.6.0;
use 5.6.0;
Also, "sprintf" and "printf" support the Perl-specific for-
mat flag %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 "Scalar value constructors" in perldata for additional
information.
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Improved Perl version numbering system
Beginning with Perl version 5.6.0, the version number con-
vention 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 v5.6.0
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.
The English module now sets $PERL_VERSION to $^V (a string
value) rather than $] (a numeric value). (This is a poten-
tial 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 "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 v5.6.0
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 $]).
New syntax for declaring subroutine attributes
Formerly, if you wanted to mark a subroutine as being a
method call or as requiring an automatic lock() when it is
entered, you had to declare that with a "use attrs" pragma
in the body of the subroutine. That can now be accomplished
with declaration syntax, like this:
sub mymethod : locked method;
...
sub mymethod : locked method {
...
}
sub othermethod :locked :method;
...
sub othermethod :locked :method {
...
}
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(Note how only the first ":" is mandatory, and whitespace
surrounding the ":" is optional.)
AutoSplit.pm and SelfLoader.pm have been updated to keep the
attributes with the stubs they provide. See attributes.
File and directory handles can be autovivified
Similar to how constructs such as "$x->[0]" autovivify a
reference, handle constructors (open(), opendir(), pipe(),
socketpair(), sysopen(), socket(), and accept()) now auto-
vivify a file or directory handle if the handle passed to
them is an uninitialized scalar variable. This allows the
constructs such as "open(my $fh, ...)" and "open(local
$fh,...)" to be used to create filehandles that will con-
veniently be closed automatically when the scope ends, pro-
vided there are no other references to them. This largely
eliminates the need for typeglobs when opening filehandles
that must be passed around, as in the following example:
sub myopen {
open my $fh, "@_"
or die "Can't open '@_': $!";
return $fh;
}
{
my $f = myopen("</etc/motd");
print <$f>;
# $f implicitly closed here
}
open() with more than two arguments
If open() is passed three arguments instead of two, the
second argument is used as the mode and the third argument
is taken to be the file name. This is primarily useful for
protecting against unintended magic behavior of the tradi-
tional two-argument form. See "open" in perlfunc.
64-bit support
Any platform that has 64-bit integers either
(1) natively as longs or ints
(2) via special compiler flags
(3) using long long or int64_t
is able to use "quads" (64-bit integers) as follows:
+ constants (decimal, hexadecimal, octal, binary) in the
code
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+ arguments to oct() and hex()
+ arguments to print(), printf() and sprintf() (flag pre-
fixes ll, L, q)
+ printed as such
+ pack() and unpack() "q" and "Q" formats
+ in basic arithmetics: + - * / % (NOTE: operating close
to the limits of the integer values may produce surpris-
ing results)
+ in bit arithmetics: & | ^ ~ << >> (NOTE: these used to
be forced to be 32 bits wide but now operate on the full
native width.)
+ vec()
Note that unless you have the case (a) you will have to con-
figure and compile Perl using the -Duse64bitint Configure
flag.
NOTE: The Configure flags -Duselonglong and -Duse64bits have been
deprecated. Use -Duse64bitint instead.
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.
The "use64bitint" 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 "64bitint" does not imply that your C
compiler will be using 64-bit "int"s (it might, but it
doesn't have to): the "use64bitint" means that you will be
able to have 64 bits wide scalar values.
The "use64bitall" 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.
Natively 64-bit systems like Alpha and Cray need neither
-Duse64bitint nor -Duse64bitall.
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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).
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.
Large file support
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.
NOTE: The default action is to enable large file support, if
available on the platform.
If the large file support is on, and you have a Fcntl con-
stant O_LARGEFILE, the O_LARGEFILE is automatically added to
the flags of sysopen().
Beware that unless your filesystem also supports "sparse
files" seeking to umpteen petabytes may be inadvisable.
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.
Finally, in addition to your process/process group maximum
filesize limits, you may have quota limits on your filesys-
tems that stop you (your user id or your user group id) from
using large files.
Adjusting your process/user/group/file system/operating sys-
tem 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.
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Long doubles
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 Con-
figure -Duselongdouble to enable this support (if it is
available).
"more bits"
You can "Configure -Dusemorebits" to turn on both the 64-bit
support and the long double support.
Enhanced support for sort() subroutines
Perl subroutines with a prototype of "($$)", 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 "sort" in perlfunc.
For unprototyped sort subroutines, the historical behavior
of passing the elements to be compared as the global vari-
ables $a and $b remains unchanged.
"sort $coderef @foo" allowed
sort() did not accept a subroutine reference as the com-
parison function in earlier versions. This is now permit-
ted.
File globbing implemented internally
Perl now uses the File::Glob implementation of the glob()
operator automatically. This avoids using an external csh
process and the problems associated with it.
NOTE: This is currently an experimental feature. Interfaces and
implementation are subject to change.
Support for CHECK blocks
In addition to "BEGIN", "INIT", "END", "DESTROY" and "AUTO-
LOAD", subroutines named "CHECK" are now special. These are
queued up during compilation and behave similar to END
blocks, except they are called at the end of compilation
rather than at the end of execution. They cannot be called
directly.
POSIX character class syntax [: :] supported
For example to match alphabetic characters use
/[[:alpha:]]/. See perlre for details.
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Better pseudo-random number generator
In 5.005_0x and earlier, perl's rand() function used the C
library rand(3) function. As of 5.005_52, Configure tests
for drand48(), random(), and rand() (in that order) and
picks the first one it finds.
These changes should result in better random numbers from
rand().
Improved "qw//" operator
The "qw//" operator is now evaluated at compile time into a
true list instead of being replaced with a run time call to
"split()". This removes the confusing misbehaviour of
"qw//" in scalar context, which had inherited that behaviour
from split().
Thus:
$foo = ($bar) = qw(a b c); print "$foo|$bar\n";
now correctly prints "3|a", instead of "2|a".
Better worst-case behavior of hashes
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 perfor-
mance on keys that are repeated sequences.
pack() format 'Z' supported
The new format type 'Z' is useful for packing and unpacking
null-terminated strings. See "pack" in perlfunc.
pack() format modifier '!' supported
The new format type modifier '!' is useful for packing and
unpacking native shorts, ints, and longs. See "pack" in
perlfunc.
pack() and unpack() support counted strings
The template character '/' can be used to specify a counted
string type to be packed or unpacked. See "pack" in perl-
func.
Comments in pack() templates
The '#' character in a template introduces a comment up to
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templates.
Weak references
In previous versions of Perl, you couldn't cache objects so
as to allow them to be deleted if the last reference from
outside the cache is deleted. The reference in the cache
would hold a reference count on the object and the objects
would never be destroyed.
Another familiar problem is with circular references. When
an object references itself, its reference count would never
go down to zero, and it would not get destroyed until the
program is about to exit.
Weak references solve this by allowing you to "weaken" any
reference, that is, make it not count towards the reference
count. When the last non-weak reference to an object is
deleted, the object is destroyed and all the weak references
to the object are automatically undef-ed.
To use this feature, you need the Devel::WeakRef package
from CPAN, which contains additional documentation.
NOTE: This is an experimental feature. Details are subject to change.
Binary numbers supported
Binary numbers are now supported as literals, in s?printf
formats, and "oct()":
$answer = 0b101010;
printf "The answer is: %b\n", oct("0b101010");
Lvalue subroutines
Subroutines can now return modifiable lvalues. See "Lvalue
subroutines" in perlsub.
NOTE: This is an experimental feature. Details are subject to change.
Some arrows may be omitted in calls through references
Perl now allows the arrow to be omitted in many constructs
involving subroutine calls through references. For example,
"$foo[10]->('foo')" may now be written "$foo[10]('foo')".
This is rather similar to how the arrow may be omitted from
"$foo[10]->{'foo'}". Note however, that the arrow is still
required for "foo(10)->('bar')".
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Boolean assignment operators are legal lvalues
Constructs such as "($a ||= 2) += 1" are now allowed.
exists() is supported on subroutine names
The exists() builtin now works on subroutine names. A sub-
routine is considered to exist if it has been declared (even
if implicitly). See "exists" in perlfunc for examples.
exists() and delete() are supported on array elements
The exists() and delete() builtins now work on simple arrays
as well. The behavior is similar to that on hash elements.
exists() 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 EXISTS() method
in the corresponding tied package will be invoked.
delete() may be used to remove an element from the array and
return it. The array element at that position returns to
its uninitialized state, so that testing for the same ele-
ment with exists() will return false. If the element hap-
pens 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 DELETE() method in the corresponding tied package will
be invoked.
See "exists" in perlfunc and "delete" in perlfunc for exam-
ples.
Pseudo-hashes work better
Dereferencing some types of reference values in a
pseudo-hash, such as "$ph->{foo}[1]", was accidentally
disallowed. This has been corrected.
When applied to a pseudo-hash element, exists() now reports
whether the specified value exists, not merely if the key is
valid.
delete() 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 "Pseudo-hashes:
Using an array as a hash" in perlref.
Pseudo-hash slices with constant keys are now optimized to
array lookups at compile-time.
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List assignments to pseudo-hash slices are now supported.
The "fields" pragma now provides ways to create
pseudo-hashes, via fields::new() and fields::phash(). See
fields.
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.
Automatic flushing of output buffers
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.
This is not supported on some platforms like Solaris where a
suitably correct implementation of fflush(NULL) isn't avail-
able.
Better diagnostics on meaningless filehandle operations
Constructs such as "open(<FH>)" and "close(<FH>)" are com-
pile 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).
Where possible, buffered data discarded from duped input
filehandle
"open(NEW, "<&OLD")" now attempts to discard any data that
was previously read and buffered in "OLD" before duping the
handle. On platforms where doing this is allowed, the next
read operation on "NEW" will return the same data as the
corresponding operation on "OLD". Formerly, it would have
returned the data from the start of the following disk block
instead.
eof() has the same old magic as <>
"eof()" would return true if no attempt to read from "<>"
had yet been made. "eof()" has been changed to have a lit-
tle magic of its own, it now opens the "<>" files.
binmode() can be used to set :crlf and :raw modes
binmode() 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 "binmode" in perlfunc and
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open.
"-T" filetest recognizes UTF-8 encoded files as "text"
The algorithm used for the "-T" filetest has been enhanced
to correctly identify UTF-8 content as "text".
system(), backticks and pipe open now reflect exec() failure
On Unix and similar platforms, system(), qx() and open(FOO,
"cmd |") etc., are implemented via fork() and exec(). When
the underlying exec() fails, earlier versions did not report
the error properly, since the exec() happened to be in a
different process.
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
$!.
Improved diagnostics
Line numbers are no longer suppressed (under most likely
circumstances) during the global destruction phase.
Diagnostics emitted from code running in threads other than
the main thread are now accompanied by the thread ID.
Embedded null characters in diagnostics now actually show
up. They used to truncate the message in prior versions.
$foo::a and $foo::b are now exempt from "possible typo"
warnings only if sort() is encountered in package "foo".
Unrecognized alphabetic escapes encountered when parsing
quote constructs now generate a warning, since they may take
on new semantics in later versions of Perl.
Many diagnostics now report the internal operation in which
the warning was provoked, like so:
Use of uninitialized value in concatenation (.) at (eval 1) line 1.
Use of uninitialized value in print at (eval 1) line 1.
Diagnostics that occur within eval may also report the file
and line number where the eval is located, in addition to
the eval sequence number and the line number within the
evaluated text itself. For example:
Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
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Diagnostics follow STDERR
Diagnostic output now goes to whichever file the "STDERR"
handle is pointing at, instead of always going to the under-
lying C runtime library's "stderr".
More consistent close-on-exec behavior
On systems that support a close-on-exec flag on filehandles,
the flag is now set for any handles created by pipe(), sock-
etpair(), 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 "pipe" in perlfunc, "socketpair" in perl-
func, "socket" in perlfunc, "accept" in perlfunc, and "$^F"
in perlvar.
syswrite() ease-of-use
The length argument of "syswrite()" has become optional.
Better syntax checks on parenthesized unary operators
Expressions such as:
print defined(&foo,&bar,&baz);
print uc("foo","bar","baz");
undef($foo,&bar);
used to be accidentally allowed in earlier versions, and
produced unpredictable behaviour. Some produced ancillary
warnings when used in this way; others silently did the
wrong thing.
The parenthesized forms of most unary operators that expect
a single argument now ensure that they are not called with
more than one argument, making the cases shown above syntax
errors. The usual behaviour of:
print defined &foo, &bar, &baz;
print uc "foo", "bar", "baz";
undef $foo, &bar;
remains unchanged. See perlop.
Bit operators support full native integer width
The bit operators (& | ^ ~ << >>) now operate on the full
native integral width (the exact size of which is available
in $Config{ivsize}). For example, if your platform is either
natively 64-bit or if Perl has been configured to use 64-bit
integers, these operations apply to 8 bytes (as opposed to 4
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bytes on 32-bit platforms). For portability, be sure to mask
off the excess bits in the result of unary "~", e.g., "~$x &
0xffffffff".
Improved security features
More potentially unsafe operations taint their results for
improved security.
The "passwd" and "shell" fields returned by the getpwent(),
getpwnam(), and getpwuid() are now tainted, because the user
can affect their own encrypted password and login shell.
The variable modified by shmread(), and messages returned by
msgrcv() (and its object-oriented interface
IPC::SysV::Msg::rcv) are also tainted, because other
untrusted processes can modify messages and shared memory
segments for their own nefarious purposes.
More functional bareword prototype (*)
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 "require" or "do".
Arguments prototyped as "*" will now be visible within the
subroutine as either a simple scalar or as a reference to a
typeglob. See "Prototypes" in perlsub.
"require" and "do" may be overridden
"require" and "do 'file'" 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 "require" will also
affect "use", provided the override is visible at
compile-time. See "Overriding Built-in Functions" in perl-
sub.
$^X variables may now have names longer than one character
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 compatibil-
ity reasons, these variables must be written with explicit
braces, as "${^XY}" for example. "${^XYZ}" is synonymous
with ${"\cXYZ"}. Variable names with more than one control
character, such as "${^XY^Z}", are illegal.
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
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variable name stops after the control character. Thus
"$^XYZ" continues to be synonymous with "$^X . "YZ"" as
before.
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 "^_", which may be
used by user programs and are guaranteed not to acquire spe-
cial meaning in any future version of Perl.
New variable $^C reflects "-c" switch
$^C has a boolean value that reflects whether perl is being
run in compile-only mode (i.e. via the "-c" switch). Since
BEGIN blocks are executed under such conditions, this vari-
able enables perl code to determine whether actions that
make sense only during normal running are warranted. See
perlvar.
New variable $^V contains Perl version as a string
$^V contains the Perl version number as a string composed of
characters whose ordinals match the version numbers, i.e.
v5.6.0. This may be used in string comparisons.
See "Support for strings represented as a vector of ordi-
nals" for an example.
Optional Y2K warnings
If Perl is built with the cpp macro "PERL_Y2KWARN" defined,
it emits optional warnings when concatenating the number 19
with another number.
This behavior must be specifically enabled when running Con-
figure. See INSTALL and README.Y2K.
Arrays now always interpolate into double-quoted strings
In double-quoted strings, arrays now interpolate, no matter
what. The behavior in earlier versions of perl 5 was that
arrays would interpolate into strings if the array had been
mentioned before the string was compiled, and otherwise Perl
would raise a fatal compile-time error. In versions 5.000
through 5.003, the error was
Literal @example now requires backslash
In versions 5.004_01 through 5.6.0, the error was
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In string, @example now must be written as \@example
The idea here was to get people into the habit of writing
"fred\@example.com" when they wanted a literal "@" sign,
just as they have always written "Give me back my \$5" when
they wanted a literal "$" sign.
Starting with 5.6.1, when Perl now sees an "@" sign in a
double-quoted string, it always attempts to interpolate an
array, regardless of whether or not the array has been used
or declared already. The fatal error has been downgraded to
an optional warning:
Possible unintended interpolation of @example in string
This warns you that "fred@example.com" is going to turn into
"fred.com" if you don't backslash the "@". See
http://www.plover.com/~mjd/perl/at-error.html for more
details about the history here.
@- and @+ provide starting/ending offsets of regex sub-
matches
The new magic variables @- and @+ provide the starting and
ending offsets, respectively, of $&, $1, $2, etc. See perl-
var for details.
Modules and Pragmata
Modules
attributes
While used internally by Perl as a pragma, this module
also provides a way to fetch subroutine and variable
attributes. See attributes.
B The Perl Compiler suite has been extensively reworked
for this release. More of the standard Perl testsuite
passes when run under the Compiler, but there is still a
significant way to go to achieve production quality com-
piled executables.
NOTE: The Compiler suite remains highly experimental. The
generated code may not be correct, even when it manages to execute
without errors.
Benchmark
Overall, Benchmark results exhibit lower average error
and better timing accuracy.
You can now run tests for n seconds instead of guessing
the right number of tests to run: e.g., timethese(-5,
...) will run each code for at least 5 CPU seconds.
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Zero as the "number of repetitions" means "for at least
3 CPU seconds". The output format has also changed.
For example:
use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
will now output something like this:
Benchmark: running a, b, each for at least 5 CPU seconds...
a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
New features: "each for at least N CPU seconds...",
"wallclock secs", and the "@ operations/CPU second
(n=operations)".
timethese() now returns a reference to a hash of Bench-
mark objects containing the test results, keyed on the
names of the tests.
timethis() now returns the iterations field in the
Benchmark result object instead of 0.
timethese(), timethis(), and the new cmpthese() (see
below) can also take a format specifier of 'none' to
suppress output.
A new function countit() is just like timeit() except
that it takes a TIME instead of a COUNT.
A new function cmpthese() prints a chart comparing the
results of each test returned from a timethese() call.
For each possible pair of tests, the percentage speed
difference (iters/sec or seconds/iter) is shown.
For other details, see Benchmark.
ByteLoader
The ByteLoader is a dedicated extension to generate and
run Perl bytecode. See ByteLoader.
constant
References can now be used.
The new version also allows a leading underscore in con-
stant names, but disallows a double leading underscore
(as in "__LINE__"). Some other names are disallowed or
warned against, including BEGIN, END, etc. Some names
which were forced into main:: used to fail silently in
some cases; now they're fatal (outside of main::) and an
optional warning (inside of main::). The ability to
detect whether a constant had been set with a given name
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has been added.
See constant.
charnames
This pragma implements the "\N" string escape. See
charnames.
Data::Dumper
A "Maxdepth" setting can be specified to avoid venturing
too deeply into deep data structures. See Data::Dumper.
The XSUB implementation of Dump() is now automatically
called if the "Useqq" setting is not in use.
Dumping "qr//" objects works correctly.
DB "DB" is an experimental module that exposes a clean
abstraction to Perl's debugging API.
DB_File
DB_File can now be built with Berkeley DB versions 1, 2
or 3. See "ext/DB_File/Changes".
Devel::DProf
Devel::DProf, a Perl source code profiler has been
added. See Devel::DProf and dprofpp.
Devel::Peek
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.
Dumpvalue
The Dumpvalue module provides screen dumps of Perl data.
DynaLoader
DynaLoader now supports a dl_unload_file() function on
platforms that support unloading shared objects using
dlclose().
Perl can also optionally arrange to unload all extension
shared objects loaded by Perl. To enable this, build
Perl with the Configure option
"-Accflags=-DDL_UNLOAD_ALL_AT_EXIT". (This maybe useful
if you are using Apache with mod_perl.)
English
$PERL_VERSION now stands for $^V (a string value) rather
than for $] (a numeric value).
Env Env now supports accessing environment variables like
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PATH as array variables.
Fcntl
More Fcntl constants added: F_SETLK64, F_SETLKW64,
O_LARGEFILE for large file (more than 4GB) access (NOTE:
the O_LARGEFILE is automatically added to sysopen()
flags if large file support has been configured, as is
the default), Free/Net/OpenBSD locking behaviour flags
F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the com-
bined mask of O_RDONLY, O_WRONLY, and O_RDWR. The
seek()/sysseek() constants SEEK_SET, SEEK_CUR, and
SEEK_END are available via the ":seek" tag. The
chmod()/stat() S_IF* constants and S_IS* functions are
available via the ":mode" tag.
File::Compare
A compare_text() function has been added, which allows
custom comparison functions. See File::Compare.
File::Find
File::Find now works correctly when the wanted() func-
tion is either autoloaded or is a symbolic reference.
A bug that caused File::Find to lose track of the work-
ing directory when pruning top-level directories has
been fixed.
File::Find now also supports several other options to
control its behavior. It can follow symbolic links if
the "follow" option is specified. Enabling the
"no_chdir" option will make File::Find skip changing the
current directory when walking directories. The
"untaint" flag can be useful when running with taint
checks enabled.
See File::Find.
File::Glob
This extension implements BSD-style file globbing. By
default, it will also be used for the internal implemen-
tation of the glob() operator. See File::Glob.
File::Spec
New methods have been added to the File::Spec module:
devnull() returns the name of the null device (/dev/null
on Unix) and tmpdir() the name of the temp directory
(normally /tmp on Unix). There are now also methods to
convert between absolute and relative filenames:
abs2rel() and rel2abs(). For compatibility with operat-
ing systems that specify volume names in file paths, the
splitpath(), splitdir(), and catdir() methods have been
added.
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File::Spec::Functions
The new File::Spec::Functions modules provides a func-
tion interface to the File::Spec module. Allows short-
hand
$fullname = catfile($dir1, $dir2, $file);
instead of
$fullname = File::Spec->catfile($dir1, $dir2, $file);
Getopt::Long
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.
Getopt::Long encourages the use of Pod::Usage to produce
help messages. For example:
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;
__END__
=head1 NAME
sample - Using Getopt::Long and Pod::Usage
=head1 SYNOPSIS
sample [options] [file ...]
Options:
-help brief help message
-man full documentation
=head1 OPTIONS
=over 8
=item B<-help>
Print a brief help message and exits.
=item B<-man>
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Prints the manual page and exits.
=back
=head1 DESCRIPTION
B<This program> will read the given input file(s) and do something
useful with the contents thereof.
=cut
See Pod::Usage for details.
A bug that prevented the non-option call-back <> from
being specified as the first argument has been fixed.
To specify the characters < and > as option starters,
use ><. Note, however, that changing option starters is
strongly deprecated.
IO write() and syswrite() will now accept a single-argument
form of the call, for consistency with Perl's
syswrite().
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
connect() manually.
A bug that prevented the IO::Socket::protocol() accessor
from ever returning the correct value has been
corrected.
IO::Socket::connect now uses non-blocking IO instead of
alarm() to do connect timeouts.
IO::Socket::accept now uses select() instead of alarm()
for doing timeouts.
IO::Socket::INET->new now sets $! correctly on failure.
$@ is still set for backwards compatibility.
JPL Java Perl Lingo is now distributed with Perl. See
jpl/README for more information.
lib "use lib" now weeds out any trailing duplicate entries.
"no lib" removes all named entries.
Math::BigInt
The bitwise operations "<<", ">>", "&", "|", and "~" are
now supported on bigints.
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Math::Complex
The accessor methods Re, Im, arg, abs, rho, and theta
can now also act as mutators (accessor $z->Re(), mutator
$z->Re(3)).
The class method "display_format" and the corresponding
object method "display_format", in addition to accepting
just one argument, now can also accept a parameter hash.
Recognized keys of a parameter hash are "style", which
corresponds to the old one parameter case, and two new
parameters: "format", which is a printf()-style format
string (defaults usually to "%.15g", you can revert to
the default by setting the format string to "undef")
used for both parts of a complex number, and
"polar_pretty_print" (defaults to true), which controls
whether an attempt is made to try to recognize small
multiples and rationals of pi (2pi, pi/2) at the argu-
ment (angle) of a polar complex number.
The potentially disruptive change is that in list con-
text both methods now return the parameter hash, instead
of only the value of the "style" parameter.
Math::Trig
A little bit of radial trigonometry (cylindrical and
spherical), radial coordinate conversions, and the great
circle distance were added.
Pod::Parser, Pod::InputObjects
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 para-
graphs and commands to user-defined methods which are
free to interpret or translate them as they see fit.
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.
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 pod-people@perl.org mailing list.
For further information, please see Pod::Parser and
Pod::InputObjects.
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Pod::Checker, podchecker
This utility checks pod files for correct syntax,
according to perlpod. Obvious errors are flagged as
such, while warnings are printed for mistakes that can
be handled gracefully. The checklist is not complete
yet. See Pod::Checker.
Pod::ParseUtils, Pod::Find
These modules provide a set of gizmos that are useful
mainly for pod translators. Pod::Find traverses direc-
tory structures and returns found pod files, along with
their canonical names (like "File::Spec::Unix").
Pod::ParseUtils contains Pod::List (useful for storing
pod list information), Pod::Hyperlink (for parsing the
contents of "L<>" sequences) and Pod::Cache (for caching
information about pod files, e.g., link nodes).
Pod::Select, podselect
Pod::Select is a subclass of Pod::Parser which provides
a function named "podselect()" to filter out user-
specified sections of raw pod documentation from an
input stream. podselect is a script that provides access
to Pod::Select from other scripts to be used as a
filter. See Pod::Select.
Pod::Usage, pod2usage
Pod::Usage provides the function "pod2usage()" to print
usage messages for a Perl script based on its embedded
pod documentation. The pod2usage() function is gen-
erally useful to all script authors since it lets them
write and maintain a single source (the pods) for docu-
mentation, thus removing the need to create and maintain
redundant usage message text consisting of information
already in the pods.
There is also a pod2usage script which can be used from
other kinds of scripts to print usage messages from pods
(even for non-Perl scripts with pods embedded in com-
ments).
For details and examples, please see Pod::Usage.
Pod::Text and Pod::Man
Pod::Text has been rewritten to use Pod::Parser. While
pod2text() is still available for backwards compatibil-
ity, the module now has a new preferred interface. See
Pod::Text for the details. The new Pod::Text module is
easily subclassed for tweaks to the output, and two such
subclasses (Pod::Text::Termcap for man-page-style bold
and underlining using termcap information, and
Pod::Text::Color for markup with ANSI color sequences)
are now standard.
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pod2man has been turned into a module, Pod::Man, which
also uses Pod::Parser. In the process, several out-
standing bugs related to quotes in section headers,
quoting of code escapes, and nested lists have been
fixed. pod2man is now a wrapper script around this
module.
SDBM_File
An EXISTS method has been added to this module (and
sdbm_exists() has been added to the underlying sdbm
library), so one can now call exists on an SDBM_File
tied hash and get the correct result, rather than a run-
time error.
A bug that may have caused data loss when more than one
disk block happens to be read from the database in a
single FETCH() has been fixed.
Sys::Syslog
Sys::Syslog now uses XSUBs to access facilities from
syslog.h so it no longer requires syslog.ph to exist.
Sys::Hostname
Sys::Hostname now uses XSUBs to call the C library's
gethostname() or uname() if they exist.
Term::ANSIColor
Term::ANSIColor is a very simple module to provide easy
and readable access to the ANSI color and highlighting
escape sequences, supported by most ANSI terminal emula-
tors. It is now included standard.
Time::Local
The timelocal() and timegm() functions used to silently
return bogus results when the date fell outside the
machine's integer range. They now consistently croak()
if the date falls in an unsupported range.
Win32
The error return value in list context has been changed
for all functions that return a list of values. Previ-
ously these functions returned a list with a single ele-
ment "undef" if an error occurred. Now these functions
return the empty list in these situations. This applies
to the following functions:
Win32::FsType
Win32::GetOSVersion
The remaining functions are unchanged and continue to
return "undef" on error even in list context.
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The Win32::SetLastError(ERROR) function has been added
as a complement to the Win32::GetLastError() function.
The new Win32::GetFullPathName(FILENAME) returns the
full absolute pathname for FILENAME in scalar context.
In list context it returns a two-element list containing
the fully qualified directory name and the filename.
See Win32.
XSLoader
The XSLoader extension is a simpler alternative to
DynaLoader. See XSLoader.
DBM Filters
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:
filter_store_key
filter_store_value
filter_fetch_key
filter_fetch_value
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 perldbmfilter for further
information.
Pragmata
"use attrs" is now obsolete, and is only provided for
backward-compatibility. It's been replaced by the "sub :
attributes" syntax. See "Subroutine Attributes" in perlsub
and attributes.
Lexical warnings pragma, "use warnings;", to control
optional warnings. See perllexwarn.
"use filetest" to control the behaviour of filetests ("-r"
"-w" ...). Currently only one subpragma implemented, "use
filetest 'access';", that uses access(2) or equivalent to
check permissions instead of using stat(2) as usual. This
matters in filesystems where there are ACLs (access control
lists): the stat(2) might lie, but access(2) knows better.
The "open" pragma can be used to specify default disciplines
for handle constructors (e.g. open()) and for qx//. The two
pseudo-disciplines ":raw" and ":crlf" are currently sup-
ported on DOS-derivative platforms (i.e. where binmode is
not a no-op). See also "binmode() can be used to set :crlf
and :raw modes".
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dprofpp
"dprofpp" is used to display profile data generated using
"Devel::DProf". See dprofpp.
find2perl
The "find2perl" utility now uses the enhanced features of
the File::Find module. The -depth and -follow options are
supported. Pod documentation is also included in the
script.
h2xs
The "h2xs" tool can now work in conjunction with "C::Scan"
(available from CPAN) to automatically parse real-life
header files. The "-M", "-a", "-k", and "-o" options are
new.
perlcc
"perlcc" now supports the C and Bytecode backends. By
default, it generates output from the simple C backend
rather than the optimized C backend.
Support for non-Unix platforms has been improved.
perldoc
"perldoc" has been reworked to avoid possible security
holes. It will not by default let itself be run as the
superuser, but you may still use the -U switch to try to
make it drop privileges first.
The Perl Debugger
Many bug fixes and enhancements were added to perl5db.pl,
the Perl debugger. The help documentation was rearranged.
New commands include "< ?", "> ?", and "{ ?" to list out
current actions, "man docpage" to run your doc viewer on
some perl docset, and support for quoted options. The help
information was rearranged, and should be viewable once
again if you're using less as your pager. A serious secu-
rity hole was plugged--you should immediately remove all
older versions of the Perl debugger as installed in previous
releases, all the way back to perl3, from your system to
avoid being bitten by this.
Improved Documentation
Many of the platform-specific README files are now part of
the perl installation. See perl for the complete list.
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perlapi.pod
The official list of public Perl API functions.
perlboot.pod
A tutorial for beginners on object-oriented Perl.
perlcompile.pod
An introduction to using the Perl Compiler suite.
perldbmfilter.pod
A howto document on using the DBM filter facility.
perldebug.pod
All material unrelated to running the Perl debugger,
plus all low-level guts-like details that risked crush-
ing the casual user of the debugger, have been relocated
from the old manpage to the next entry below.
perldebguts.pod
This new manpage contains excessively low-level material
not related to the Perl debugger, but slightly related
to debugging Perl itself. It also contains some arcane
internal details of how the debugging process works that
may only be of interest to developers of Perl debuggers.
perlfork.pod
Notes on the fork() emulation currently available for
the Windows platform.
perlfilter.pod
An introduction to writing Perl source filters.
perlhack.pod
Some guidelines for hacking the Perl source code.
perlintern.pod
A list of internal functions in the Perl source code.
(List is currently empty.)
perllexwarn.pod
Introduction and reference information about lexically
scoped warning categories.
perlnumber.pod
Detailed information about numbers as they are
represented in Perl.
perlopentut.pod
A tutorial on using open() effectively.
perlreftut.pod
A tutorial that introduces the essentials of references.
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perltootc.pod
A tutorial on managing class data for object modules.
perltodo.pod
Discussion of the most often wanted features that may
someday be supported in Perl.
perlunicode.pod
An introduction to Unicode support features in Perl.
Performance enhancements
Simple sort() using { $a <=> $b } and the like are optimized
Many common sort() operations using a simple inlined block
are now optimized for faster performance.
Optimized assignments to lexical variables
Certain operations in the RHS of assignment statements have
been optimized to directly set the lexical variable on the
LHS, eliminating redundant copying overheads.
Faster subroutine calls
Minor changes in how subroutine calls are handled internally
provide marginal improvements in performance.
delete(), each(), values() and hash iteration are faster
The hash values returned by delete(), each(), values() and
hashes in a list context are the actual values in the hash,
instead of copies. This results in significantly better per-
formance, because it eliminates needless copying in most
situations.
Installation and Configuration Improvements-Dusethreads means something different
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".
As of v5.6.0, interpreter-threads support is still lacking a
way to create new threads from Perl (i.e., "use Thread;"
will not work with interpreter threads). "use Thread;" con-
tinues to be available when you specify the -Duse5005threads
option to Configure, bugs and all.
NOTE: Support for threads continues to be an experimental feature.
Interfaces and implementation are subject to sudden and drastic changes.
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New Configure flags
The following new flags may be enabled on the Configure com-
mand line by running Configure with "-Dflag".
usemultiplicity
usethreads useithreads (new interpreter threads: no Perl API yet)
usethreads use5005threads (threads as they were in 5.005)
use64bitint (equal to now deprecated 'use64bits')
use64bitall
uselongdouble
usemorebits
uselargefiles
usesocks (only SOCKS v5 supported)
Threadedness and 64-bitness now more daring
The Configure options enabling the use of threads and the
use of 64-bitness are now more daring in the sense that they
no more have an explicit list of operating systems of known
threads/64-bit capabilities. In other words: if your
operating system has the necessary APIs and datatypes, you
should be able just to go ahead and use them, for threads by
Configure -Dusethreads, and for 64 bits either explicitly by
Configure -Duse64bitint or implicitly if your system has
64-bit wide datatypes. See also "64-bit support".
Long Doubles
Some platforms have "long doubles", floating point numbers
of even larger range than ordinary "doubles". To enable
using long doubles for Perl's scalars, use -Duselongdouble.
-Dusemorebits
You can enable both -Duse64bitint and -Duselongdouble with
-Dusemorebits. See also "64-bit support".
-Duselargefiles
Some platforms support system APIs that are capable of han-
dling large files (typically, files larger than two giga-
bytes). Perl will try to use these APIs if you ask for
-Duselargefiles.
See "Large file support" for more information.
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installusrbinperl
You can use "Configure -Uinstallusrbinperl" which causes
installperl to skip installing perl also as /usr/bin/perl.
This is useful if you prefer not to modify /usr/bin for some
reason or another but harmful because many scripts assume to
find Perl in /usr/bin/perl.
SOCKS support
You can use "Configure -Dusesocks" which causes Perl to
probe for the SOCKS proxy protocol library (v5, not v4).
For more information on SOCKS, see:
http://www.socks.nec.com/
"-A" flag
You can "post-edit" the Configure variables using the Con-
figure "-A" switch. The editing happens immediately after
the platform specific hints files have been processed but
before the actual configuration process starts. Run "Con-
figure -h" to find out the full "-A" syntax.
Enhanced Installation Directories
The installation structure has been enriched to improve the
support for maintaining multiple versions of perl, to pro-
vide locations for vendor-supplied modules, scripts, and
manpages, and to ease maintenance of locally-added modules,
scripts, and manpages. See the section on Installation
Directories in the INSTALL file for complete details. For
most users building and installing from source, the defaults
should be fine.
If you previously used "Configure -Dsitelib" or "-Dsitearch"
to set special values for library directories, you might
wish to consider using the new "-Dsiteprefix" setting
instead. Also, if you wish to re-use a config.sh file from
an earlier version of perl, you should be sure to check that
Configure makes sensible choices for the new directories.
See INSTALL for complete details.
gcc automatically tried if 'cc' does not seem to be working
In many platforms the vendor-supplied 'cc' is too stripped-
down to build Perl (basically, the 'cc' doesn't do ANSI C).
If this seems to be the case and the 'cc' does not seem to
be the GNU C compiler 'gcc', an automatic attempt is made to
find and use 'gcc' instead.
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Supported platforms
+ The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported
by the Thread extension.
+ GNU/Hurd is now supported.
+ Rhapsody/Darwin is now supported.
+ EPOC is now supported (on Psion 5).
+ The cygwin port (formerly cygwin32) has been greatly
improved.
DOS
+ Perl now works with djgpp 2.02 (and 2.03 alpha).
+ Environment variable names are not converted to upper-
case any more.
+ Incorrect exit codes from backticks have been fixed.
+ This port continues to use its own builtin globbing (not
File::Glob).
OS390 (OpenEdition MVS)
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.
It is unclear whether future versions will renew support for
this platform, but the possibility exists.
VMS
Numerous revisions and extensions to configuration, build,
testing, and installation process to accommodate core
changes and VMS-specific options.
Expand %ENV-handling code to allow runtime mapping to logi-
cal names, CLI symbols, and CRTL environ array.
Extension of subprocess invocation code to accept filespecs
as command "verbs".
Add to Perl command line processing the ability to use
default file types and to recognize Unix-style "2>&1".
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Expansion of File::Spec::VMS routines, and integration into
ExtUtils::MM_VMS.
Extension of ExtUtils::MM_VMS to handle complex extensions
more flexibly.
Barewords at start of Unix-syntax paths may be treated as
text rather than only as logical names.
Optional secure translation of several logical names used
internally by Perl.
Miscellaneous bugfixing and porting of new core code to VMS.
Thanks are gladly extended to the many people who have con-
tributed VMS patches, testing, and ideas.
Win32
Perl can now emulate fork() internally, using multiple
interpreters running in different concurrent threads. This
support must be enabled at build time. See perlfork for
detailed information.
When given a pathname that consists only of a drivename,
such as "A:", opendir() and stat() now use the current work-
ing directory for the drive rather than the drive root.
The builtin XSUB functions in the Win32:: namespace are
documented. See Win32.
$^X now contains the full path name of the running execut-
able.
A Win32::GetLongPathName() function is provided to comple-
ment Win32::GetFullPathName() and Win32::GetShortPathName().
See Win32.
POSIX::uname() is supported.
system(1,...) now returns true process IDs rather than pro-
cess handles. kill() accepts any real process id, rather
than strictly return values from system(1,...).
For better compatibility with Unix, "kill(0, $pid)" can now
be used to test whether a process exists.
The "Shell" module is supported.
Better support for building Perl under command.com in Win-
dows 95 has been added.
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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.
The glob() operator is implemented via the "File::Glob"
extension, which supports glob syntax of the C shell. This
increases the flexibility of the glob() operator, but there
may be compatibility issues for programs that relied on the
older globbing syntax. If you want to preserve compatibil-
ity with the older syntax, you might want to run perl with
"-MFile::DosGlob". For details and compatibility informa-
tion, see File::Glob.
Significant bug fixes
<HANDLE> on empty files
With $/ set to "undef", "slurping" an empty file returns a
string of zero length (instead of "undef", as it used to)
the first time the HANDLE is read after $/ is set to
"undef". Further reads yield "undef".
This means that the following will append "foo" to an empty
file (it used to do nothing):
perl -0777 -pi -e 's/^/foo/' empty_file
The behaviour of:
perl -pi -e 's/^/foo/' empty_file
is unchanged (it continues to leave the file empty).
"eval '...'" improvements
Line numbers (as reflected by caller() and most diagnostics)
within "eval '...'" were often incorrect where here docu-
ments were involved. This has been corrected.
Lexical lookups for variables appearing in "eval '...'"
within functions that were themselves called within an "eval
'...'" were searching the wrong place for lexicals. The
lexical search now correctly ends at the subroutine's block
boundary.
The use of "return" within "eval {...}" caused $@ not to be
reset correctly when no exception occurred within the eval.
This has been fixed.
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Parsing of here documents used to be flawed when they
appeared as the replacement expression in "eval
's/.../.../e'". This has been fixed.
All compilation errors are true errors
Some "errors" encountered at compile time were by necessity
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.
The mechanism for reporting such errors has been reimple-
mented to queue compile-time errors and report them at the
end of the compilation as true errors rather than as warn-
ings. This fixes cases where error messages leaked through
in the form of warnings when code was compiled at run time
using "eval STRING", and also allows such errors to be reli-
ably trapped using "eval "..."".
Implicitly closed filehandles are safer
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.
Behavior of list slices is more consistent
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.
The new behavior is to produce an empty list if (and only
if) the original list was empty. Consider the following
example:
@a = (1,undef,undef,2)[2,1,2];
The old behavior would have resulted in @a having no ele-
ments. The new behavior ensures it has three undefined ele-
ments.
Note in particular that the behavior of slices of the fol-
lowing cases remains unchanged:
@a = ()[1,2];
@a = (getpwent)[7,0];
@a = (anything_returning_empty_list())[2,1,2];
@a = @b[2,1,2];
@a = @c{'a','b','c'};
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See perldata.
"(\$)" prototype and $foo{a}
A scalar reference prototype now correctly allows a hash or
array element in that slot.
"goto &sub" and AUTOLOAD
The "goto &sub" construct works correctly when &sub happens
to be autoloaded.
"-bareword" allowed under "use integer"
The autoquoting of barewords preceded by "-" did not work in
prior versions when the "integer" pragma was enabled. This
has been fixed.
Failures in DESTROY()
When code in a destructor threw an exception, it went unno-
ticed in earlier versions of Perl, unless someone happened
to be looking in $@ just after the point the destructor hap-
pened to run. Such failures are now visible as warnings
when warnings are enabled.
Locale bugs fixed
printf() and sprintf() previously reset the numeric locale
back to the default "C" locale. This has been fixed.
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.
Memory leaks
The "eval 'return sub {...}'" construct could sometimes leak
memory. This has been fixed.
Operations that aren't filehandle constructors used to leak
memory when used on invalid filehandles. This has been
fixed.
Constructs that modified @_ could fail to deallocate values
in @_ and thus leak memory. This has been corrected.
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Spurious subroutine stubs after failed subroutine calls
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.
Taint failures under "-U"
When running in unsafe mode, taint violations could some-
times cause silent failures. This has been fixed.
END blocks and the "-c" switch
Prior versions used to run BEGIN and 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 "-c" switch is used, or if compilation fails.
See "Support for CHECK blocks" for how to run things when
the compile phase ends.
Potential to leak DATA filehandles
Using the "__DATA__" 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.
This caveat is now better explained in the documentation.
See perldata.
New or Changed Diagnostics
"%s" variable %s masks earlier declaration in same %s
(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.
"my sub" not yet implemented
(F) Lexically scoped subroutines are not yet imple-
mented. Don't try that yet.
"our" variable %s redeclared
(W misc) You seem to have already declared the same glo-
bal once before in the current lexical scope.
'!' allowed only after types %s
(F) The '!' is allowed in pack() and unpack() only after
certain types. See "pack" in perlfunc.
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/ cannot take a count
(F) You had an unpack template indicating a counted-
length string, but you have also specified an explicit
size for the string. See "pack" in perlfunc.
/ must be followed by a, A or Z
(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 "pack" in perlfunc.
/ must be followed by a*, A* or Z*
(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 "pack" in perlfunc.
/ must follow a numeric type
(F) You had an unpack template that contained a '#', but
this did not follow some numeric unpack specification.
See "pack" in perlfunc.
/%s/: Unrecognized escape \\%c passed through
(W regexp) You used a backslash-character combination
which is not recognized by Perl. This combination
appears in an interpolated variable or a "'"-delimited
regular expression. The character was understood
literally.
/%s/: Unrecognized escape \\%c in character class passed through
(W regexp) You used a backslash-character combination
which is not recognized by Perl inside character
classes. The character was understood literally.
/%s/ should probably be written as "%s"
(W syntax) You have used a pattern where Perl expected
to find a string, as in the first argument to "join".
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.
%s() called too early to check prototype
(W prototype) You've called a function that has a proto-
type 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 pro-
totype 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 warn-
ing. See perlsub.
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%s argument is not a HASH or ARRAY element
(F) The argument to exists() must be a hash or array
element, such as:
$foo{$bar}
$ref->{"susie"}[12]
%s argument is not a HASH or ARRAY element or slice
(F) The argument to delete() must be either a hash or
array element, such as:
$foo{$bar}
$ref->{"susie"}[12]
or a hash or array slice, such as:
@foo[$bar, $baz, $xyzzy]
@{$ref->[12]}{"susie", "queue"}
%s argument is not a subroutine name
(F) The argument to exists() for "exists &sub" must be a
subroutine name, and not a subroutine call. "exists
&sub()" will generate this error.
%s package attribute may clash with future reserved word: %s
(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 attributes.
(in cleanup) %s
(W misc) This prefix usually indicates that a DESTROY()
method raised the indicated exception. Since destruc-
tors are usually called by the system at arbitrary
points during execution, and often a vast number of
times, the warning is issued only once for any number of
failures that would otherwise result in the same message
being repeated.
Failure of user callbacks dispatched using the
"G_KEEPERR" flag could also result in this warning. See
"G_KEEPERR" in perlcall.
<> should be quotes
(F) You wrote "require <file>" when you should have
written "require 'file'".
Attempt to join self
(F) You tried to join a thread from within itself, which
is an impossible task. You may be joining the wrong
thread, or you may need to move the join() to some other
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thread.
Bad evalled substitution pattern
(F) You've used the /e switch to evaluate the replace-
ment for a substitution, but perl found a syntax error
in the code to evaluate, most likely an unexpected right
brace '}'.
Bad realloc() ignored
(S) An internal routine called realloc() on something
that had never been malloc()ed in the first place. Man-
datory, but can be disabled by setting environment vari-
able "PERL_BADFREE" to 1.
Bareword found in conditional
(W bareword) 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:
open FOO || die;
It may also indicate a misspelled constant that has been
interpreted as a bareword:
use constant TYPO => 1;
if (TYOP) { print "foo" }
The "strict" pragma is useful in avoiding such errors.
Binary number > 0b11111111111111111111111111111111 non-
portable
(W portable) The binary number you specified is larger
than 2**32-1 (4294967295) and therefore non-portable
between systems. See perlport for more on portability
concerns.
Bit vector size > 32 non-portable
(W portable) Using bit vector sizes larger than 32 is
non-portable.
Buffer overflow in prime_env_iter: %s
(W internal) A warning peculiar to VMS. While Perl was
preparing to iterate over %ENV, it encountered a logical
name or symbol definition which was too long, so it was
truncated to the string shown.
Can't check filesystem of script "%s"
(P) For some reason you can't check the filesystem of
the script for nosuid.
Can't declare class for non-scalar %s in "%s"
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(S) Currently, only scalar variables can declared with a
specific class qualifier in a "my" or "our" declaration.
The semantics may be extended for other types of vari-
ables in future.
Can't declare %s in "%s"
(F) Only scalar, array, and hash variables may be
declared as "my" or "our" variables. They must have
ordinary identifiers as names.
Can't ignore signal CHLD, forcing to default
(W signal) Perl has detected that it is being run with
the SIGCHLD signal (sometimes known as SIGCLD) disabled.
Since disabling this signal will interfere with proper
determination of exit status of child processes, Perl
has reset the signal to its default value. This situa-
tion typically indicates that the parent program under
which Perl may be running (e.g., cron) is being very
careless.
Can't modify non-lvalue subroutine call
(F) Subroutines meant to be used in lvalue context
should be declared as such, see "Lvalue subroutines" in
perlsub.
Can't read CRTL environ
(S) A warning peculiar to VMS. Perl tried to read an
element of %ENV from the CRTL's internal environment
array and discovered the array was missing. You need to
figure out where your CRTL misplaced its environ or
define PERL_ENV_TABLES (see perlvms) so that environ is
not searched.
Can't remove %s: %s, skipping file
(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.
Can't return %s from lvalue subroutine
(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.
Can't weaken a nonreference
(F) You attempted to weaken something that was not a
reference. Only references can be weakened.
Character class [:%s:] unknown
(F) The class in the character class [: :] syntax is
unknown. See perlre.
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Character class syntax [%s] belongs inside character classes
(W unsafe) The character class constructs [: :], [= =],
and [. .] go inside 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.
Constant is not %s reference
(F) A constant value (perhaps declared using the "use
constant" 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 "Constant Functions" in perlsub and constant.
constant(%s): %s
(F) The parser found inconsistencies either while
attempting to define an overloaded constant, or when
trying to find the character name specified in the
"\N{...}" escape. Perhaps you forgot to load the
corresponding "overload" or "charnames" pragma? See
charnames and overload.
CORE::%s is not a keyword
(F) The CORE:: namespace is reserved for Perl keywords.
array) is deprecated@u-3p defined(@array) is deprecated
(D) defined() is not usually useful on arrays because it
checks for an undefined scalar value. If you want to
see if the array is empty, just use "if (@array) { # not
empty }" for example.
defined(%hash) is deprecated
(D) defined() is not usually useful on hashes because it
checks for an undefined scalar value. If you want to
see if the hash is empty, just use "if (%hash) { # not
empty }" for example.
Did not produce a valid header
See Server error.
(Did you mean "local" instead of "our"?)
(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.
Document contains no data
See Server error.
entering effective %s failed
(F) While under the "use filetest" pragma, switching the
real and effective uids or gids failed.
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false [] range "%s" in regexp
(W regexp) A character class range must start and end at
a literal character, not another character class like
"\d" or "[:alpha:]". The "-" in your false range is
interpreted as a literal "-". Consider quoting the "-",
"\-". See perlre.
Filehandle %s opened only for output
(W io) You tried to read from a filehandle opened only
for writing. If you intended it to be a read/write
filehandle, you needed to open it with "+<" or "+>" or
"+>>" instead of with "<" or nothing. If you intended
only to read from the file, use "<". See "open" in
perlfunc.
flock() on closed filehandle %s
(W closed) The filehandle you're attempting to flock()
got itself closed some time before now. Check your
logic flow. flock() operates on filehandles. Are you
attempting to call flock() on a dirhandle by the same
name?
Global symbol "%s" requires explicit package name
(F) You've said "use strict vars", which indicates that
all variables must either be lexically scoped (using
"my"), declared beforehand using "our", or explicitly
qualified to say which package the global variable is in
(using "::").
Hexadecimal number > 0xffffffff non-portable
(W portable) The hexadecimal number you specified is
larger than 2**32-1 (4294967295) and therefore non-
portable between systems. See perlport for more on por-
tability concerns.
Ill-formed CRTL environ value "%s"
(W internal) A warning peculiar to VMS. Perl tried to
read the CRTL's internal environ array, and encountered
an element without the "=" delimiter used to separate
keys from values. The element is ignored.
Ill-formed message in prime_env_iter: |%s|
(W internal) A warning peculiar to VMS. Perl tried to
read a logical name or CLI symbol definition when
preparing to iterate over %ENV, and didn't see the
expected delimiter between key and value, so the line
was ignored.
Illegal binary digit %s
(F) You used a digit other than 0 or 1 in a binary
number.
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Illegal binary digit %s ignored
(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.
Illegal number of bits in vec
(F) The number of bits in vec() (the third argument)
must be a power of two from 1 to 32 (or 64, if your
platform supports that).
Integer overflow in %s number
(W overflow) The hexadecimal, octal or binary number you
have specified either as a literal or as an argument to
hex() or oct() 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 opera-
tions.
Invalid %s attribute: %s
The indicated attribute for a subroutine or variable was
not recognized by Perl or by a user-supplied handler.
See attributes.
Invalid %s attributes: %s
The indicated attributes for a subroutine or variable
were not recognized by Perl or by a user-supplied
handler. See attributes.
invalid [] range "%s" in regexp
The offending range is now explicitly displayed.
Invalid separator character %s in attribute list
(F) Something other than a colon or whitespace was seen
between the elements of an attribute list. If the pre-
vious attribute had a parenthesised parameter list,
perhaps that list was terminated too soon. See attri-
butes.
Invalid separator character %s in subroutine attribute list
(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 too soon.
leaving effective %s failed
(F) While under the "use filetest" pragma, switching the
real and effective uids or gids failed.
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Lvalue subs returning %s not implemented yet
(F) Due to limitations in the current implementation,
array and hash values cannot be returned in subroutines
used in lvalue context. See "Lvalue subroutines" in
perlsub.
Method %s not permitted
See Server error.
Missing %sbrace%s on \N{}
(F) Wrong syntax of character name literal
"\N{charname}" within double-quotish context.
Missing command in piped open
(W pipe) You used the "open(FH, "| command")" or
"open(FH, "command |")" construction, but the command
was missing or blank.
Missing name in "my sub"
(F) The reserved syntax for lexically scoped subroutines
requires that they have a name with which they can be
found.
No %s specified for -%c
(F) The indicated command line switch needs a mandatory
argument, but you haven't specified one.
No package name allowed for variable %s in "our"
(F) Fully qualified variable names are not allowed in
"our" declarations, because that doesn't make much sense
under existing semantics. Such syntax is reserved for
future extensions.
No space allowed after -%c
(F) The argument to the indicated command line switch
must follow immediately after the switch, without inter-
vening spaces.
no UTC offset information; assuming local time is UTC
(S) A warning peculiar to VMS. Perl was unable to find
the local timezone offset, so it's assuming that local
system time is equivalent to UTC. If it's not, define
the logical name SYS$TIMEZONE_DIFFERENTIAL to translate
to the number of seconds which need to be added to UTC
to get local time.
Octal number > 037777777777 non-portable
(W portable) The octal number you specified is larger
than 2**32-1 (4294967295) and therefore non-portable
between systems. See perlport for more on portability
concerns.
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See also perlport for writing portable code.
panic: del_backref
(P) Failed an internal consistency check while trying to
reset a weak reference.
panic: kid popen errno read
(F) forked child returned an incomprehensible message
about its errno.
panic: magic_killbackrefs
(P) Failed an internal consistency check while trying to
reset all weak references to an object.
Parentheses missing around "%s" list
(W parenthesis) You said something like
my $foo, $bar = @_;
when you meant
my ($foo, $bar) = @_;
Remember that "my", "our", and "local" bind tighter than
comma.
Possible unintended interpolation of %s in string
(W ambiguous) It used to be that Perl would try to guess
whether you wanted an array interpolated or a literal @.
It no longer does this; arrays are now always interpo-
lated into strings. This means that if you try some-
thing like:
print "fred@example.com";
and the array @example doesn't exist, Perl is going to
print "fred.com", which is probably not what you wanted.
To get a literal "@" sign in a string, put a backslash
before it, just as you would to get a literal "$" sign.
Possible Y2K bug: %s
(W y2k) You are concatenating the number 19 with another
number, which could be a potential Year 2000 problem.
pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
(W deprecated) You have written something like this:
sub doit
{
use attrs qw(locked);
}
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You should use the new declaration syntax instead.
sub doit : locked
{
...
The "use attrs" pragma is now obsolete, and is only pro-
vided for backward-compatibility. See "Subroutine Attri-
butes" in perlsub.
Premature end of script headers
See Server error.
Repeat count in pack overflows
(F) You can't specify a repeat count so large that it
overflows your signed integers. See "pack" in perlfunc.
Repeat count in unpack overflows
(F) You can't specify a repeat count so large that it
overflows your signed integers. See "unpack" in perl-
func.
realloc() of freed memory ignored
(S) An internal routine called realloc() on something
that had already been freed.
Reference is already weak
(W misc) You have attempted to weaken a reference that
is already weak. Doing so has no effect.
setpgrp can't take arguments
(F) Your system has the setpgrp() from BSD 4.2, which
takes no arguments, unlike POSIX setpgid(), which takes
a process ID and process group ID.
Strange *+?{} on zero-length expression
(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 "/abc(?=(?:xyz){3})/", not "/abc(?=xyz){3}/".
switching effective %s is not implemented
(F) While under the "use filetest" pragma, we cannot
switch the real and effective uids or gids.
This Perl can't reset CRTL environ elements (%s)
This Perl can't set CRTL environ elements (%s=%s)
(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
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CRTL that contained the setenv() function. You'll need
to rebuild Perl with a CRTL that does, or redefine
PERL_ENV_TABLES (see perlvms) so that the environ array
isn't the target of the change to %ENV which produced
the warning.
Too late to run %s block
(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
"require" or "do" when you should be using "use"
instead. Or perhaps you should put the "require" or
"do" inside a BEGIN block.
Unknown open() mode '%s'
(F) The second argument of 3-argument open() is not
among the list of valid modes: "<", ">", ">>", "+<",
"+>", "+>>", "-|", "|-".
Unknown process %x sent message to prime_env_iter: %s
(P) An error peculiar to VMS. Perl was reading values
for %ENV before iterating over it, and someone else
stuck a message in the stream of data Perl expected.
Someone's very confused, or perhaps trying to subvert
Perl's population of %ENV for nefarious purposes.
Unrecognized escape \\%c passed through
(W misc) You used a backslash-character combination
which is not recognized by Perl. The character was
understood literally.
Unterminated attribute parameter in attribute list
(F) The lexer saw an opening (left) parenthesis charac-
ter while parsing an attribute list, but the matching
closing (right) parenthesis character was not found.
You may need to add (or remove) a backslash character to
get your parentheses to balance. See attributes.
Unterminated attribute list
(F) The lexer found something other than a simple iden-
tifier at the start of an attribute, and it wasn't a
semicolon or the start of a block. Perhaps you ter-
minated the parameter list of the previous attribute too
soon. See attributes.
Unterminated attribute parameter in subroutine attribute list
(F) The lexer saw an opening (left) parenthesis charac-
ter while parsing a subroutine attribute list, but the
matching closing (right) parenthesis character was not
found. You may need to add (or remove) a backslash
character to get your parentheses to balance.
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Unterminated subroutine attribute list
(F) The lexer found something other than a simple iden-
tifier at the start of a subroutine attribute, and it
wasn't a semicolon or the start of a block. Perhaps you
terminated the parameter list of the previous attribute
too soon.
Value of CLI symbol "%s" too long
(W misc) A warning peculiar to VMS. Perl tried to read
the value of an %ENV element from a CLI symbol table,
and found a resultant string longer than 1024 charac-
ters. The return value has been truncated to 1024 char-
acters.
Version number must be a constant number
(P) The attempt to translate a "use Module n.n LIST"
statement into its equivalent "BEGIN" block found an
internal inconsistency with the version number.
New tests
lib/attrs
Compatibility tests for "sub : attrs" vs the older "use
attrs".
lib/env
Tests for new environment scalar capability (e.g., "use
Env qw($BAR);").
lib/env-array
Tests for new environment array capability (e.g., "use
Env qw(@PATH);").
lib/io_const
IO constants (SEEK_*, _IO*).
lib/io_dir
Directory-related IO methods (new, read, close, rewind,
tied delete).
lib/io_multihomed
INET sockets with multi-homed hosts.
lib/io_poll
IO poll().
lib/io_unix
UNIX sockets.
op/attrs
Regression tests for "my ($x,@y,%z) : attrs" and <sub :
attrs>.
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op/filetest
File test operators.
op/lex_assign
Verify operations that access pad objects (lexicals and
temporaries).
op/exists_sub
Verify "exists &sub" operations.
Incompatible Changes
Perl Source Incompatibilities
Beware that any new warnings that have been added or old
ones that have been enhanced are not considered incompatible
changes.
Since all new warnings must be explicitly requested via the
"-w" switch or the "warnings" pragma, it is ultimately the
programmer's responsibility to ensure that warnings are
enabled judiciously.
CHECK is a new keyword
All subroutine definitions named CHECK are now special.
See "/"Support for CHECK blocks"" for more information.
Treatment of list slices of undef has changed
There is a potential incompatibility in the behavior of
list slices that are comprised entirely of undefined
values. See "Behavior of list slices is more con-
sistent".
Format of $English::PERL_VERSION is different
The English module now sets $PERL_VERSION to $^V (a
string value) rather than $] (a numeric value). This is
a potential incompatibility. Send us a report via perl-
bug if you are affected by this.
See "Improved Perl version numbering system" for the
reasons for this change.
Literals of the form 1.2.3 parse differently
Previously, numeric literals with more than one dot in
them were interpreted as a floating point number con-
catenated with one or more numbers. Such "numbers" are
now parsed as strings composed of the specified ordi-
nals.
For example, "print 97.98.99" used to output 97.9899 in
earlier versions, but now prints "abc".
See "Support for strings represented as a vector of
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ordinals".
Possibly changed pseudo-random number generator
Perl programs that depend on reproducing a specific set
of pseudo-random numbers may now produce different out-
put due to improvements made to the rand() builtin. You
can use "sh Configure -Drandfunc=rand" to obtain the old
behavior.
See "Better pseudo-random number generator".
Hashing function for hash keys has changed
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 different from that of
previous versions, especially when iterating on hashes.
See "Better worst-case behavior of hashes" for addi-
tional information.
"undef" fails on read only values
Using the "undef" operator on a readonly value (such as
$1) has the same effect as assigning "undef" to the
readonly value--it throws an exception.
Close-on-exec bit may be set on pipe and socket handles
Pipe and socket handles are also now subject to the
close-on-exec behavior determined by the special vari-
able $^F.
See "More consistent close-on-exec behavior".
Writing "$$1" to mean "${$}1" is unsupported
Perl 5.004 deprecated the interpretation of $$1 and
similar within interpolated strings to mean "$$ . "1"",
but still allowed it.
In Perl 5.6.0 and later, "$$1" always means "${$1}".
delete(), each(), values() and "\(%h)"
operate on aliases to values, not copies
delete(), each(), values() and hashes (e.g. "\(%h)") 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 differ-
ence when creating references to the returned values.
Keys in the hash are still returned as copies when
iterating on a hash.
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See also "delete(), each(), values() and hash iteration
are faster".
vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
vec() generates a run-time error if the BITS argument is
not a valid power-of-two integer.
Text of some diagnostic output has changed
Most references to internal Perl operations in diagnos-
tics 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.
"%@"Thesundocumenteddspecial variable "%@" that used to
accumulate "background" errors (such as those that hap-
pen in DESTROY()) has been removed, because it could
potentially result in memory leaks.
Parenthesized not() behaves like a list operator
The "not" operator now falls under the "if it looks like
a function, it behaves like a function" rule.
As a result, the parenthesized form can be used with
"grep" and "map". The following construct used to be a
syntax error before, but it works as expected now:
grep not($_), @things;
On the other hand, using "not" with a literal list slice
may not work. The following previously allowed con-
struct:
print not (1,2,3)[0];
needs to be written with additional parentheses now:
print not((1,2,3)[0]);
The behavior remains unaffected when "not" is not fol-
lowed by parentheses.
Semantics of bareword prototype "(*)" have changed
The semantics of the bareword prototype "*" have
changed. Perl 5.005 always coerced simple scalar argu-
ments 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 a simple scalar or as a
reference to a typeglob.
See "More functional bareword prototype (*)".
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Semantics of bit operators may have changed on 64-bit platforms
If your platform is either natively 64-bit or if Perl
has been configured to used 64-bit integers, i.e.,
$Config{ivsize} is 8, there may be a potential incompa-
tibility in the behavior of bitwise numeric operators (&
| ^ ~ << >>). These operators used to strictly operate
on the lower 32 bits of integers in previous versions,
but now operate over the entire native integral width.
In particular, note that unary "~" will produce dif-
ferent results on platforms that have different
$Config{ivsize}. For portability, be sure to mask off
the excess bits in the result of unary "~", e.g., "~$x &
0xffffffff".
See "Bit operators support full native integer width".
More builtins taint their results
As described in "Improved security features", there may
be more sources of taint in a Perl program.
To avoid these new tainting behaviors, you can build
Perl with the Configure option
"-Accflags=-DINCOMPLETE_TAINTS". Beware that the ensu-
ing perl binary may be insecure.
C Source Incompatibilities
"PERL_POLLUTE"
Release 5.005 grandfathered old global symbol names by
providing preprocessor macros for extension source com-
patibility. As of release 5.6.0, these preprocessor
definitions are not available by default. You need to
explicitly compile perl with "-DPERL_POLLUTE" to get
these definitions. For extensions still using the old
symbols, this option can be specified via MakeMaker:
perl Makefile.PL POLLUTE=1
"PERL_IMPLICIT_CONTEXT"
This new build option provides a set of macros for all
API functions such that an implicit interpreter/thread
context argument is passed to every API function. As a
result of this, something like "sv_setsv(foo,bar)"
amounts to a macro invocation that actually translates
to something like "Perl_sv_setsv(my_perl,foo,bar)".
While this is generally expected to not have any signi-
ficant source compatibility issues, the difference
between a macro and a real function call will need to be
considered.
This means that there is a source compatibility issue as
a result of this if your extensions attempt to use
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pointers to any of the Perl API functions.
Note that the above issue is not relevant to the default
build of Perl, whose interfaces continue to match those
of prior versions (but subject to the other options
described here).
See "The Perl API" in perlguts for detailed information
on the ramifications of building Perl with this option.
NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
with one of -Dusethreads, -Dusemultiplicity, or both. It is not
intended to be enabled by users at this time.
"PERL_POLLUTE_MALLOC"
Enabling Perl's malloc in release 5.005 and earlier
caused the namespace of the system's malloc family of
functions to be usurped by the Perl versions, since by
default they used the same names. Besides causing prob-
lems on platforms that do not allow these functions to
be cleanly replaced, this also meant that the system
versions could not be called in programs that used
Perl's malloc. Previous versions of Perl have allowed
this behaviour to be suppressed with the HIDEMYMALLOC
and EMBEDMYMALLOC preprocessor definitions.
As of release 5.6.0, Perl's malloc family of functions
have default names distinct from the system versions.
You need to explicitly compile perl with
"-DPERL_POLLUTE_MALLOC" to get the older behaviour.
HIDEMYMALLOC and EMBEDMYMALLOC have no effect, since the
behaviour they enabled is now the default.
Note that these functions do not constitute Perl's
memory allocation API. See "Memory Allocation" in perl-
guts for further information about that.
Compatible C Source API Changes
"PATCHLEVEL" is now "PERL_VERSION"
The cpp macros "PERL_REVISION", "PERL_VERSION", and
"PERL_SUBVERSION" are now available by default from
perl.h, and reflect the base revision, patchlevel, and
subversion respectively. "PERL_REVISION" had no prior
equivalent, while "PERL_VERSION" and "PERL_SUBVERSION"
were previously available as "PATCHLEVEL" and "SUBVER-
SION".
The new names cause less pollution of the cpp namespace
and reflect what the numbers have come to stand for in
common practice. For compatibility, the old names are
still supported when patchlevel.h is explicitly included
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(as required before), so there is no source incompati-
bility from the change.
Binary Incompatibilities
In general, the default build of this release is expected to
be binary compatible for extensions built with the 5.005
release or its maintenance versions. However, specific
platforms may have broken binary compatibility due to
changes in the defaults used in hints files. Therefore,
please be sure to always check the platform-specific README
files for any notes to the contrary.
The usethreads or usemultiplicity builds are not binary com-
patible with the corresponding builds in 5.005.
On platforms that require an explicit list of exports (AIX,
OS/2 and Windows, among others), purely internal symbols
such as parser functions and the run time opcodes are not
exported by default. Perl 5.005 used to export all func-
tions irrespective of whether they were considered part of
the public API or not.
For the full list of public API functions, see perlapi.
Known Problems
Localizing a tied hash element may leak memory
As of the 5.6.1 release, there is a known leak when code
such as this is executed:
use Tie::Hash;
tie my %tie_hash => 'Tie::StdHash';
...
local($tie_hash{Foo}) = 1; # leaks
Known test failures
+ 64-bit builds
Subtest #15 of lib/b.t may fail under 64-bit builds on
platforms such as HP-UX PA64 and Linux IA64. The issue
is still being investigated.
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).
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Note that 64-bit support is still experimental.
+ Failure of Thread tests
The subtests 19 and 20 of lib/thr5005.t test are known
to fail due to fundamental problems in the 5.005 thread-
ing implementation. These are not new failures--Perl
5.005_0x has the same bugs, but didn't have these tests.
(Note that support for 5.005-style threading remains
experimental.)
+ NEXTSTEP 3.3 POSIX test failure
In NEXTSTEP 3.3p2 the implementation of the strftime(3)
in the operating system libraries is buggy: the %j for-
mat 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.
+ Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test
failure with gcc
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.
EBCDIC platforms not fully supported
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.
The 5.6.1 release improves support for EBCDIC platforms, but
they are not fully supported yet.
UNICOS/mk CC failures during Configure run
In UNICOS/mk the following errors may appear during the Con-
figure run:
Guessing which symbols your C compiler and preprocessor define...
CC-20 cc: ERROR File = try.c, Line = 3
...
bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
...
4 errors detected in the compilation of "try.c".
The culprit is the broken awk of UNICOS/mk. The effect is
fortunately rather mild: Perl itself is not adversely
affected by the error, only the h2ph utility coming with
Perl, and that is rather rarely needed these days.
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Arrow operator and arrays
When the left argument to the arrow operator "->" is an
array, or the "scalar" operator operating on an array, the
result of the operation must be considered erroneous. For
example:
@x->[2]
scalar(@x)->[2]
These expressions will get run-time errors in some future
release of Perl.
Experimental features
As discussed above, many features are still experimental.
Interfaces and implementation of these features are subject
to change, and in extreme cases, even subject to removal in
some future release of Perl. These features include the
following:
Threads
Unicode
64-bit support
Lvalue subroutines
Weak references
The pseudo-hash data type
The Compiler suite
Internal implementation of file globbing
The DB module
The regular expression code constructs:
"(?{ code })" and "(??{ code })"
Obsolete Diagnostics
Character class syntax [: :] is reserved for future extensions
(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: "\[:" and ":\]".
Ill-formed logical name |%s| in prime_env_iter
(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.
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\@%s@u-3p In string, @%s now must be written as \@%s
The description of this error used to say:
(Someday it will simply assume that an unbackslashed @
interpolates an array.)
That day has come, and this fatal error has been
removed. It has been replaced by a non-fatal warning
instead. See "Arrays now always interpolate into
double-quoted strings" for details.
Probable precedence problem on %s
(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 con-
struct, for example:
open FOO || die;
regexp too big
(F) The current implementation of regular expressions
uses shorts as address offsets within a string. Unfor-
tunately this means that if the regular expression com-
piles 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
perlre.
Use of "$$<digit>" to mean "${$}<digit>" is deprecated
(D) Perl versions before 5.004 misinterpreted any type
marker followed by "$" and a digit. For example, "$$0"
was incorrectly taken to mean "${$}0" instead of
"${$0}". This bug is (mostly) fixed in Perl 5.004.
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.
Reporting Bugs
If you find what you think is a bug, you might check the
articles recently posted to the comp.lang.perl.misc news-
group. There may also be information at http://www.perl.com/
, the Perl Home Page.
If you believe you have an unreported bug, please run the
perlbug program included with your release. Be sure to trim
your bug down to a tiny but sufficient test case. Your bug
report, along with the output of "perl -V", will be sent off
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to perlbug@perl.org to be analysed by the Perl porting team.
SEE ALSO
The Changes file for exhaustive details on what changed.
The INSTALL file for how to build Perl.
The README file for general stuff.
The Artistic and Copying files for copyright information.
HISTORY
Written by Gurusamy Sarathy <gsar@ActiveState.com>, with
many contributions from The Perl Porters.
Send omissions or corrections to <perlbug@perl.org>.
perl v5.8.8 2006-06-30 69
