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PERL561DELTA(1)
NAME
perl561delta - 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 platforms 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 Problems" 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.
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 pessimised 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 situations. This is now
avoided.
Match variables $1 et al., weren't being unset when a pattern match was
backtracking, and the anomaly showed up inside "/...(?{ ... }).../"
etc. These variables are now tracked correctly.
pos() did not return the correct value within s///ge in earlier
versions. This is now handled correctly.
"slurp" mode
readline() on files opened in "slurp" mode could return an extra "" at
the end in certain situations. This has been corrected.
Autovivification of symbolic references to special variables
Autovivification of symbolic references of special variables described
in perlvar (as in "${$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 redefinition 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 rationalized. It does not
taint the result of floating point formats anymore, making the behavior
consistent with that of string interpolation.
sort()
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 performance 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. Previously, 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.
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 version 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 whitespace" (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 tabulator 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 continues 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 subroutines 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.
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.
· 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 documentation 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.
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. Various 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
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.
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 supported 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 propagated 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 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 support 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 interpreter, 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 reachable 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
locking 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, 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 character strings.
The "utf8" and "bytes" pragmas are used to control this support in the
current lexical scope. See perlunicode, 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 complete 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.
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 $^V magic variable (which contains the perl
version as a string), such literals can be used as a readable way to check
if you're running a particular version of Perl:
# this will parse in older versions of Perl also
if ($^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 format 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.
Improved Perl version numbering system
Beginning with Perl version 5.6.0, the version number convention has been
changed to a "dotted integer" scheme that is more commonly found in open
source projects.
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 potential incompatibility. Send us
a report via perlbug if you are affected by this.)
The v1.2.3 syntax is also now legal in Perl. See "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 $]).
New syntax for declaring subroutine attributes
Formerly, if you wanted to mark a subroutine as being a method call or as
requiring an automatic lock() when it is entered, you had to declare that
with a "use attrs" pragma in the body of the subroutine. That can now be
accomplished with declaration syntax, like this:
sub mymethod : locked method;
...
sub mymethod : locked method {
...
}
sub othermethod :locked :method;
...
sub othermethod :locked :method {
...
}
(Note how only the first ":" is mandatory, and whitespace surrounding the
":" is optional.)
AutoSplit.pm and SelfLoader.pm have been updated to keep the attributes
with the stubs they provide. See attributes.
File and directory handles can be autovivified
Similar to how constructs such as "$x->[0]" autovivify a reference, handle
constructors (open(), opendir(), pipe(), socketpair(), sysopen(), socket(),
and accept()) now autovivify 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 conveniently be closed automatically when
the scope ends, provided 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
traditional 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
· arguments to oct() and hex()
· arguments to print(), printf() and sprintf() (flag prefixes 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 surprising 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 configure 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.
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 constant 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 filesystems that stop you (your user id
or your user group id) from using large files.
Adjusting your process/user/group/file system/operating system limits is
outside the scope of Perl core language. For process limits, you may try
increasing the limits using your shell's limits/limit/ulimit command before
running Perl. The BSD::Resource extension (not included with the standard
Perl distribution) may also be of use, it offers the getrlimit/setrlimit
interface that can be used to adjust process resource usage limits,
including the maximum filesize limit.
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 Configure -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 variables $a and $b remains
unchanged.
"sort $coderef @foo" allowed
sort() did not accept a subroutine reference as the comparison function in
earlier versions. This is now permitted.
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 "AUTOLOAD",
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.
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 performance 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 perlfunc.
Comments in pack() templates
The '#' character in a template introduces a comment up to end of the line.
This facilitates documentation of pack() 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')".
Boolean assignment operators are legal lvalues
Constructs such as "($a ||= 2) += 1" are now allowed.
exists() is supported on subroutine names
The exists() builtin now works on subroutine names. A subroutine is
considered to exist if it has been declared (even if implicitly). See
"exists" in perlfunc for examples.
exists() and delete() are supported on array elements
The exists() and delete() builtins now work on simple arrays as well. The
behavior is similar to that on hash elements.
exists() can be used to check whether an array element has been
initialized. This avoids autovivifying array elements that don't exist.
If the array is tied, the EXISTS() method in the corresponding tied package
will be invoked.
delete() may be used to remove an element from the array and return it.
The array element at that position returns to its uninitialized state, so
that testing for the same element with exists() will return false. If the
element happens to be the one at the end, the size of the array also
shrinks up to the highest element that tests true for exists(), or 0 if
none such is found. If the array is tied, the DELETE() method in the
corresponding tied package will be invoked.
See "exists" in perlfunc and "delete" in perlfunc for examples.
Pseudo-hashes work better
Dereferencing some types of reference values in a pseudo-hash, such as
"$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.
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 available.
Better diagnostics on meaningless filehandle operations
Constructs such as "open(<FH>)" and "close(<FH>)" are compile time errors.
Attempting to read from filehandles that were opened only for writing will
now produce warnings (just as writing to read-only filehandles does).
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 little 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 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
Diagnostics follow STDERR
Diagnostic output now goes to whichever file the "STDERR" handle is
pointing at, instead of always going to the underlying 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(), socketpair(), socket(), and
accept(), if that is warranted by the value of $^F that may be in effect.
Earlier versions neglected to set the flag for handles created with these
operators. See "pipe" in perlfunc, "socketpair" in perlfunc, "socket" in
perlfunc, "accept" in perlfunc, and "$^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 $Config{ivsize}). For
example, if your platform is either natively 64-bit or if Perl has been
configured to use 64-bit integers, these operations apply to 8 bytes (as
opposed to 4 bytes on 32-bit platforms). For portability, be sure to mask
off the excess bits in the result of unary "~", e.g., "~$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 perlsub.
$^X variables may now have names longer than one character
Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax error.
Now variable names that begin with a control character may be arbitrarily
long. However, for compatibility reasons, these variables must be written
with explicit braces, as "${^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 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
special 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 variable 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
$^V contains the Perl version number as a string composed of characters
whose ordinals match the version numbers, i.e. v5.6.0. This may be used in
string comparisons.
See "Support for strings represented as a vector of ordinals" for an
example.
Optional Y2K warnings
If Perl is built with the cpp macro "PERL_Y2KWARN" defined, it emits
optional warnings when concatenating the number 19 with another number.
This behavior must be specifically enabled when running Configure. See
INSTALL and README.Y2K.
Arrays now always interpolate into double-quoted strings
In double-quoted strings, arrays now interpolate, no matter what. The
behavior in earlier versions of perl 5 was that arrays would interpolate
into strings if the array had been mentioned before the string was
compiled, and otherwise Perl would raise a fatal compile-time error. In
versions 5.000 through 5.003, the error was
Literal @example now requires backslash
In versions 5.004_01 through 5.6.0, the error was
In string, @example now must be written as \@example
The idea here was to get people into the habit of writing
"fred\@example.com" when they wanted a literal "@" sign, just as they have
always written "Give me back my \$5" when they wanted a literal "$" 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 submatches
The new magic variables @- and @+ provide the starting and ending offsets,
respectively, of $&, $1, $2, etc. See perlvar for details.
Modules and Pragmata
Modules
attributes
While used internally by Perl as a pragma, this module also provides a
way to fetch subroutine and variable attributes. See attributes.
B The Perl Compiler suite has been extensively reworked for this release.
More of the standard Perl testsuite passes when run under the Compiler,
but there is still a significant way to go to achieve production
quality compiled executables.
NOTE: The Compiler suite remains highly experimental. The
generated code may not be correct, even when it manages to execute
without errors.
Benchmark
Overall, Benchmark results exhibit lower average error and better
timing accuracy.
You can now run tests for n seconds instead of guessing the right
number of tests to run: e.g., timethese(-5, ...) will run each code for
at least 5 CPU seconds. Zero as the "number of repetitions" means "for
at least 3 CPU seconds". The output format has also changed. For
example:
use Benchmark;$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 Benchmark 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 constant 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 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 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 combined 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() function is either
autoloaded or is a symbolic reference.
A bug that caused File::Find to lose track of the working 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 implementation 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 operating systems that specify
volume names in file paths, the splitpath(), splitdir(), and catdir()
methods have been added.
File::Spec::Functions
The new File::Spec::Functions modules provides a function interface to
the File::Spec module. Allows shorthand
$fullname = catfile($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>
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.
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 argument (angle) of a polar complex number.
The potentially disruptive change is that in list context 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 paragraphs 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.
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 directory 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 generally useful to all script authors since it
lets them write and maintain a single source (the pods) for
documentation, 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 comments).
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 compatibility, 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.
pod2man has been turned into a module, Pod::Man, which also uses
Pod::Parser. In the process, several outstanding 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
runtime 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 emulators. 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. Previously these functions
returned a list with a single element "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.
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 supported 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".
Utility Changes
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 security 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.
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 crushing 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.
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 performance, 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;" continues 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.
New Configure flags
The following new flags may be enabled on the Configure command 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 handling large files
(typically, files larger than two gigabytes). Perl will try to use these
APIs if you ask for -Duselargefiles.
See "Large file support" for more information.
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 Configure "-A"
switch. The editing happens immediately after the platform specific hints
files have been processed but before the actual configuration process
starts. Run "Configure -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 provide 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.
Platform specific changes
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 uppercase 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 logical 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".
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 contributed 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 working 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 executable.
A Win32::GetLongPathName() function is provided to complement
Win32::GetFullPathName() and Win32::GetShortPathName(). See Win32.
POSIX::uname() is supported.
system(1,...) now returns true process IDs rather than process 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 Windows 95 has been
added.
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 compatibility
with the older syntax, you might want to run perl with "-MFile::DosGlob".
For details and compatibility information, 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 documents 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.
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 reimplemented to queue
compile-time errors and report them at the end of the compilation as true
errors rather than as warnings. This fixes cases where error messages
leaked through in the form of warnings when code was compiled at run time
using "eval STRING", and also allows such errors to be reliably 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 elements. The new
behavior ensures it has three undefined elements.
Note in particular that the behavior of slices of the following 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'};
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 unnoticed in earlier
versions of Perl, unless someone happened to be looking in $@ just after
the point the destructor happened 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.
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 sometimes 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 implemented. Don't try
that yet.
"our" variable %s redeclared
(W misc) You seem to have already declared the same global 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.
/ 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 prototype before the
parser saw a definition or declaration for it, and Perl could not check
that the call conforms to the prototype. You need to either add an
early prototype declaration for the subroutine in question, or move the
subroutine definition ahead of the call to get proper prototype
checking. Alternatively, if you are certain that you're calling the
function correctly, you may put an ampersand before the name to avoid
the warning. See perlsub.
%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 destructors 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 thread.
Bad evalled substitution pattern
(F) You've used the /e switch to evaluate the replacement 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. Mandatory, but can be disabled by
setting environment variable "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"
(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 variables 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
situation 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.
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.
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.
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 portability 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.
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
operations.
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 previous attribute had a
parenthesised parameter list, perhaps that list was terminated too
soon. See attributes.
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.
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