|
perldelta - what's new for perl v5.6.x |
open() with more than two argumentssort() subroutinessort $coderef @foo allowedqw// operatorpack() format 'Z' supportedpack() format modifier '!' supportedpack() and unpack() support counted stringspack() templatesexists() is supported on subroutine namesexists() and delete() are supported on array elementseof() has the same old magic as <>binmode() can be used to set :crlf and :raw modes-T filetest recognizes UTF-8 encoded files as ``text''exec() failuresyswrite() ease-of-userequire and do may be overridden-c switchsort() using { $a <=> $b } and the like are optimizedvalues() and hash iteration are faster-A flageval '...' improvements(\$) prototype and $foo{a}goto &sub and AUTOLOAD-bareword allowed under use integerDESTROY()-U-c switch
perldelta - what's new for perl v5.6.x
This document describes differences between the 5.005 release and the 5.6.1 release.
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 the perlhack manpage for pointers to online resources where you can inspect the individual patches described by these changes.
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/.
This is not an exhaustive list. It is intended to cover only the significant user-visible changes.
UNIVERSAL::isa()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.
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)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.
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.
readline() on files opened in ``slurp'' mode could return an extra ``'' at
the end in certain situations. This has been corrected.
${$num}) was accidentally disabled. This works
again now.
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.
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()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.
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()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.
eval "...".
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.
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.
chop()chop(@list) in list context returned the characters chopped in reverse
order. This has been reversed to be in the right order.
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 the perlfunc manpage.
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.
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.
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.
untie() will now call an UNTIE() hook if it exists. See the perltie manpage
for details.
The -DT command line switch outputs copious tokenizing information.
See the perlrun manpage.
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.
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:
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.
README.aix, README.solaris and README.macos have been added. README.posix-bc has been renamed to README.bs2000. These are installed as the perlaix manpage, the perlsolaris manpage, the perlmacos manpage, and the perlbs2000 manpage 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.
The following modules have been added.
The following modules have been upgraded.
sort() them, etc.
fmod() function supports modulus operations. Various bug fixes
have also been included.
ping() could fail on odd number of data bytes, and when the echo service
isn't running. This has been corrected.
The following new ports are now available.
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.
MacOS 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 the perlvms manpage.
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 the perlfork manpage for known bugs and caveats.
waitpid($pid, &POSIX::WNOHANG).
accept() has been fixed.
waitpid() and backticks now return the correct exit status under
Windows 9x.
chdir() and Cwd::cwd() have also been fixed.
fork() correctly returns undef and sets EAGAIN when it runs out of
pseudo-process handles.
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.
=head1 Core Enhancements
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 the perlfork manpage 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.
You can now control the granularity of warnings emitted by perl at a finer
level using the use warnings pragma. the warnings manpage and the perllexwarn manpage
have copious documentation on this feature.
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 the perlunicode manpage, the utf8 manpage and the bytes manpage 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.
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.
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 the perlfunc manpage.
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 the perldata manpage for additional information.
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 $]).
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 the attributes manpage.
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 argumentsIf 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 the perlfunc manpage.
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:
oct() and hex()
printf() and sprintf() (flag prefixes ll, L, q)
pack() and unpack() ``q'' and ``Q'' formats
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 ints (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.
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.
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).
You can ``Configure -Dusemorebits'' to turn on both the 64-bit support and the long double support.
sort() subroutinesPerl 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 the perlfunc manpage.
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 allowedsort() did not accept a subroutine reference as the comparison
function in earlier versions. This is now permitted.
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.
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.
For example to match alphabetic characters use /[[:alpha:]]/. See the perlre manpage for details.
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().
qw// operatorThe 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''.
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' supportedThe new format type 'Z' is useful for packing and unpacking null-terminated strings. See pack in the perlfunc manpage.
pack() format modifier '!' supportedThe new format type modifier '!' is useful for packing and unpacking native shorts, ints, and longs. See pack in the perlfunc manpage.
pack() and unpack() support counted stringsThe template character '/' can be used to specify a counted string type to be packed or unpacked. See pack in the perlfunc manpage.
pack() templatesThe '#' character in a template introduces a comment up to
end of the line. This facilitates documentation of pack()
templates.
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 WeakRef package from CPAN, which contains additional documentation.
NOTE: This is an experimental feature. Details are subject to change.
Binary numbers are now supported as literals, in s?printf formats, and
oct():
$answer = 0b101010;
printf "The answer is: %b\n", oct("0b101010");
Subroutines can now return modifiable lvalues. See Lvalue subroutines in the perlsub manpage.
NOTE: This is an experimental feature. Details are subject to change.
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').
Constructs such as ($a ||= 2) += 1 are now allowed.
exists() is supported on subroutine namesThe exists() builtin now works on subroutine names. A subroutine
is considered to exist if it has been declared (even if implicitly).
See exists in the perlfunc manpage for examples.
exists() and delete() are supported on array elementsThe 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 the perlfunc manpage and delete in the perlfunc manpage for examples.
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 the perlref manpage.
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 the fields manpage.
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.
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.
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).
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 modesbinmode() 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 the perlfunc manpage and the open manpage.
-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''.
exec() failureOn 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 $!.
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
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.
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 the perlfunc manpage, socketpair in the perlfunc manpage, socket in the perlfunc manpage, accept in the perlfunc manpage, and $^F in the perlvar manpage.
syswrite() ease-of-useThe length argument of syswrite() has become optional.
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 the perlop manpage.
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.
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.
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 the perlsub manpage.
require and do may be overriddenrequire 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 the perlsub manpage.
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.
-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 the perlvar manpage.
$^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.
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.
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.
NOTE: The Compiler suite remains highly experimental. The
generated code may not be correct, even when it manages to execute
without errors.
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 the Benchmark manpage.
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 the constant manpage.
\N string escape. See the charnames manpage.
Maxdepth setting can be specified to avoid venturing
too deeply into deep data structures. See the Data::Dumper manpage.
The XSUB implementation of Dump() is now automatically called if the
Useqq setting is not in use.
Dumping qr// objects works correctly.
DB is an experimental module that exposes a clean abstraction
to Perl's debugging API.
ext/DB_File/Changes.
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.)
$^V (a string value) rather than for $]
(a numeric value).
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.
compare_text() function has been added, which allows custom
comparison functions. See the File::Compare manpage.
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.
glob()
operator. See the File::Glob manpage.
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.
$fullname = catfile($dir1, $dir2, $file);
instead of
$fullname = File::Spec->catfile($dir1, $dir2, $file);
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 the Pod::Usage manpage 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.
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.
use lib now weeds out any trailing duplicate entries.
no lib removes all named entries.
<<, >>, &, |,
and ~ are now supported on bigints.
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.
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 the Pod::Parser manpage and the Pod::InputObjects manpage.
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).
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 the Pod::Usage manpage.
pod2text() is
still available for backwards compatibility, the module now has a new
preferred interface. See the Pod::Text manpage 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_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.
gethostname() or
uname() if they exist.
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.
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 the Win32 manpage.
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 the perldbmfilter manpage for further information.
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 the perlsub manpage and the attributes manpage.
Lexical warnings pragma, use warnings;, to control optional warnings.
See the perllexwarn manpage.
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.
dprofpp is used to display profile data generated using Devel::DProf.
See the dprofpp manpage.
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.
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 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 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.
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.
Many of the platform-specific README files are now part of the perl installation. See the perl manpage for the complete list.
fork() emulation currently available for the Windows platform.
open() effectively.
sort() using { $a <=> $b } and the like are optimizedMany common sort() operations using a simple inlined block are now
optimized for faster performance.
Certain operations in the RHS of assignment statements have been optimized to directly set the lexical variable on the LHS, eliminating redundant copying overheads.
Minor changes in how subroutine calls are handled internally provide marginal improvements in performance.
values() and hash iteration are fasterThe 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.
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.
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)
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.
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.
You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits. See also 64-bit support.
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.
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.
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 flagYou 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.
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.
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.
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.
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.
Perl can now emulate fork() internally, using multiple interpreters running
in different concurrent threads. This support must be enabled at build
time. See the perlfork manpage 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 the Win32 manpage.
$^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 the Win32 manpage.
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 the File::Glob manpage.
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 '...' improvementsLine 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.
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 "...".
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.
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 the perldata manpage.
(\$) prototype and $foo{a}A scalar reference prototype now correctly allows a hash or array element in that slot.
goto &sub and AUTOLOADThe goto &sub construct works correctly when &sub happens
to be autoloaded.
-bareword allowed under use integerThe autoquoting of barewords preceded by - did not work
in prior versions when the integer pragma was enabled.
This has been fixed.
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.
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.
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.
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.
-UWhen running in unsafe mode, taint violations could sometimes cause silent failures. This has been fixed.
-c switchPrior 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.
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 the perldata manpage.
pack() and unpack() only after certain types.
See pack in the perlfunc manpage.
'-delimited regular expression. The character was understood literally.
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.
exists() must be a hash or array element, such as:
$foo{$bar}
$ref->{"susie"}[12]
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"}
exists() for exists &sub must be a subroutine
name, and not a subroutine call. exists &sub() will generate this error.
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 the perlcall manpage.
require <file> when you should have written
require 'file'.
join() to some other thread.
realloc() ignoredrealloc() 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.
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.
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 the perlsub manpage and the constant manpage.
\N{...} escape. Perhaps you forgot to load the corresponding
overload or charnames pragma? See the charnames manpage and the overload manpage.
defined(@array) is deprecateddefined() 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 deprecateddefined() 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.
use filetest pragma, switching the real and
effective uids or gids failed.
\d or [:alpha:]. The ``-'' in your false
range is interpreted as a literal ``-''. Consider quoting the ``-'', ``\-''.
See the perlre manpage.
flock() on closed filehandle %sflock() 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?
= delimiter
used to separate keys from values. The element is ignored.
vec() (the third argument) must be a power of
two from 1 to 32 (or 64, if your platform supports that).
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.
use filetest pragma, switching the real and
effective uids or gids failed.
\N{charname} within
double-quotish context.
open(FH, "| command") or open(FH, "command |")
construction, but the command was missing or blank.
See also the perlport manpage for writing portable code.
my $foo, $bar = @_;
when you meant
my ($foo, $bar) = @_;
Remember that ``my'', ``our'', and ``local'' bind tighter than comma.
print "fred@example.com";
and the array @example doesn't exist, Perl is going to print
fred.com, which is probably not what you wanted. To get a literal
@ sign in a string, put a backslash before it, just as you would
to get a literal $ sign.
sub doit
{
use attrs qw(locked);
}
You should use the new declaration syntax instead.
sub doit : locked
{
...
The use attrs pragma is now obsolete, and is only provided for
backward-compatibility. See Subroutine Attributes in the perlsub manpage.
realloc() of freed memory ignoredrealloc() on something that had already
been freed.
setpgrp() from BSD 4.2, which takes no arguments,
unlike POSIX setpgid(), which takes a process ID and process group ID.
/abc(?=(?:xyz){3})/, not /abc(?=xyz){3}/.
use filetest pragma, we cannot switch the
real and effective uids or gids.
setenv() function. You'll need to
rebuild Perl with a CRTL that does, or redefine PERL_ENV_TABLES (see
the perlvms manpage) so that the environ array isn't the target of the change to
%ENV which produced the warning.
require or do when you should be using
use instead. Or perhaps you should put the require or do
inside a BEGIN block.
open() mode '%s'open() is not among the list
of valid modes: <, >, >>, +<,
+>, +>>, -|, |-.
use Module n.n LIST statement into
its equivalent BEGIN block found an internal inconsistency with
the version number.
sub : attrs vs the older use attrs.
use Env qw($BAR);).
use Env qw(@PATH);).
my ($x,@y,%z) : attrs and <sub : attrs>.
exists &sub operations.
Beware that any new warnings that have been added or old ones that have been enhanced are not considered incompatible changes.
Since all new warnings must be explicitly requested via the -w
switch or the warnings pragma, it is ultimately the programmer's
responsibility to ensure that warnings are enabled judiciously.
/"Support for CHECK blocks" for more information.
$] (a numeric value). This is a potential incompatibility.
Send us a report via perlbug if you are affected by this.
See Improved Perl version numbering system for the reasons for this change.
1.2.3 parse differentlyFor example, print 97.98.99 used to output 97.9899 in earlier
versions, but now prints abc.
See Support for strings represented as a vector of ordinals.
rand() builtin. You can use sh Configure -Drandfunc=rand to obtain
the old behavior.
See Better worst-case behavior of hashes for additional information.
undef fails on read only valuesundef operator on a readonly value (such as $1) has
the same effect as assigning undef to the readonly value--it
throws an exception.
"$$1" to mean "${$}1" is unsupported$$1 and
similar within interpolated strings to mean $$ . "1",
but still allowed it.
In Perl 5.6.0 and later, "$$1" always means "${$1}".
values() and \(%h)delete(), each(), values() and hashes (e.g. \(%h))
in a list context return the actual
values in the hash, instead of copies (as they used to in earlier
versions). Typical idioms for using these constructs copy the
returned values, but this can make a significant difference when
creating references to the returned values. Keys in the hash are still
returned as copies when iterating on a hash.
See also delete(), each(), values() and hash iteration are faster.
vec(EXPR,OFFSET,BITS) enforces powers-of-two BITSvec() generates a run-time error if the BITS argument is not
a valid power-of-two integer.
%@ has been removed%@ that used to accumulate
``background'' errors (such as those that happen in DESTROY())
has been removed, because it could potentially result in memory
leaks.
not() behaves like a list operatornot operator now falls under the ``if it looks like a function,
it behaves like a function'' rule.
As a result, the parenthesized form can be used with grep and map.
The following construct used to be a syntax error before, but it works
as expected now:
grep not($_), @things;
On the other hand, using not with a literal list slice may not
work. The following previously allowed construct:
print not (1,2,3)[0];
needs to be written with additional parentheses now:
print not((1,2,3)[0]);
The behavior remains unaffected when not is not followed by parentheses.
(*) have changed* have changed. Perl 5.005
always coerced simple scalar arguments to a typeglob, which wasn't useful
in situations where the subroutine must distinguish between a simple
scalar and a typeglob. The new behavior is to not coerce bareword
arguments to a typeglob. The value will always be visible as either
a simple scalar or as a reference to a typeglob.
~ will produce different results on platforms that have
different $Config{ivsize}. For portability, be sure to mask off
the excess bits in the result of unary ~, e.g., ~$x & 0xffffffff.
To avoid these new tainting behaviors, you can build Perl with the
Configure option -Accflags=-DINCOMPLETE_TAINTS. Beware that the
ensuing perl binary may be insecure.
PERL_POLLUTE-DPERL_POLLUTE to get these definitions. For
extensions still using the old symbols, this option can be
specified via MakeMaker:
perl Makefile.PL POLLUTE=1
PERL_IMPLICIT_CONTEXTsv_setsv(foo,bar)
amounts to a macro invocation that actually translates to something like
Perl_sv_setsv(my_perl,foo,bar). While this is generally expected
to not have any significant source compatibility issues, the difference
between a macro and a real function call will need to be considered.
This means that there is a source compatibility issue as a result of this if your extensions attempt to use pointers to any of the Perl API functions.
Note that the above issue is not relevant to the default build of Perl, whose interfaces continue to match those of prior versions (but subject to the other options described here).
See The Perl API in the perlguts manpage for detailed information on the ramifications of building Perl with this option.
NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
with one of -Dusethreads, -Dusemultiplicity, or both. It is not
intended to be enabled by users at this time.
PERL_POLLUTE_MALLOCAs of release 5.6.0, Perl's malloc family of functions have default names
distinct from the system versions. You need to explicitly compile perl with
-DPERL_POLLUTE_MALLOC to get the older behaviour. HIDEMYMALLOC
and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
the default.
Note that these functions do not constitute Perl's memory allocation API. See Memory Allocation in the perlguts manpage for further information about that.
PATCHLEVEL is now PERL_VERSIONPERL_REVISION, PERL_VERSION, and PERL_SUBVERSION
are now available by default from perl.h, and reflect the base revision,
patchlevel, and subversion respectively. PERL_REVISION had no
prior equivalent, while PERL_VERSION and PERL_SUBVERSION were
previously available as PATCHLEVEL and SUBVERSION.
The new names cause less pollution of the cpp namespace and reflect what the numbers have come to stand for in common practice. For compatibility, the old names are still supported when patchlevel.h is explicitly included (as required before), so there is no source incompatibility from the change.
In general, the default build of this release is expected to be binary compatible for extensions built with the 5.005 release or its maintenance versions. However, specific platforms may have broken binary compatibility due to changes in the defaults used in hints files. Therefore, please be sure to always check the platform-specific README files for any notes to the contrary.
The usethreads or usemultiplicity builds are not binary compatible with the corresponding builds in 5.005.
On platforms that require an explicit list of exports (AIX, OS/2 and Windows, among others), purely internal symbols such as parser functions and the run time opcodes are not exported by default. Perl 5.005 used to export all functions irrespective of whether they were considered part of the public API or not.
For the full list of public API functions, see the perlapi manpage.
As of the 5.6.1 release, there is a known leak when code such as this is executed:
use Tie::Hash;
tie my %tie_hash => 'Tie::StdHash';
...
local($tie_hash{Foo}) = 1; # leaks
The lib/io_multihomed test may hang in HP-UX if Perl has been configured to be 64-bit. Because other 64-bit platforms do not hang in this test, HP-UX is suspect. All other tests pass in 64-bit HP-UX. The test attempts to create and connect to ``multihomed'' sockets (sockets which have multiple IP addresses).
Note that 64-bit support is still experimental.
strftime(3) in the
operating system libraries is buggy: the %j format numbers the days of
a month starting from zero, which, while being logical to programmers,
will cause the subtests 19 to 27 of the lib/posix test may fail.
In earlier releases of Perl, EBCDIC environments like OS390 (also known as Open Edition MVS) and VM-ESA were supported. Due to changes required by the UTF-8 (Unicode) support, the EBCDIC platforms are not supported in Perl 5.6.0.
The 5.6.1 release improves support for EBCDIC platforms, but they are not fully supported yet.
In UNICOS/mk the following errors may appear during the Configure run:
Guessing which symbols your C compiler and preprocessor define...
CC-20 cc: ERROR File = try.c, Line = 3
...
bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
...
4 errors detected in the compilation of "try.c".
The culprit is the broken awk of UNICOS/mk. The effect is fortunately rather mild: Perl itself is not adversely affected by the error, only the h2ph utility coming with Perl, and that is rather rarely needed these days.
When the left argument to the arrow operator -> is an array, or
the scalar operator operating on an array, the result of the
operation must be considered erroneous. For example:
@x->[2]
scalar(@x)->[2]
These expressions will get run-time errors in some future release of Perl.
As discussed above, many features are still experimental. Interfaces and implementation of these features are subject to change, and in extreme cases, even subject to removal in some future release of Perl. These features include the following:
(?{ code }) and (??{ code })
(Someday it will simply assume that an unbackslashed @
interpolates an array.)
That day has come, and this fatal error has been removed. It has been replaced by a non-fatal warning instead. See Arrays now always interpolate into double-quoted strings for details.
open FOO || die;
However, the developers of Perl 5.004 could not fix this bug completely, because at least two widely-used modules depend on the old meaning of ``$$0'' in a string. So Perl 5.004 still interprets ``$$<digit>'' in the old (broken) way inside strings; but it generates this message as a warning. And in Perl 5.005, this special treatment will cease.
If you find what you think is a bug, you might check the articles recently posted to the comp.lang.perl.misc newsgroup. There may also be information at http://www.perl.com/, the Perl Home Page.
If you believe you have an unreported bug, please run the perlbug
program included with your release. Be sure to trim your bug down
to a tiny but sufficient test case. Your bug report, along with the
output of perl -V, will be sent off to perlbug@perl.org to be
analysed by the Perl porting team.
The Changes file for exhaustive details on what changed.
The INSTALL file for how to build Perl.
The README file for general stuff.
The Artistic and Copying files for copyright information.
Written by Gurusamy Sarathy <gsar@ActiveState.com>, with many contributions from The Perl Porters.
Send omissions or corrections to <perlbug@perl.org>.
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