open()
with more than two arguments
sort() subroutines
sort
$coderef @foo allowed
qw//
operator
pack()
format 'Z' supported
pack()
format modifier '!' supported
pack()
and unpack() support counted strings
pack() templates
exists()
is supported on subroutine names
exists()
and delete() are supported on array elements
eof()
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() failure
syswrite()
ease-of-use
require
and do may be overridden
-c
switch
eval
'...' improvements
(\$)
prototype and $foo{a}
goto
&sub and AUTOLOAD
-bareword
allowed under use integer
DESTROY()
-U
-c
switch
perldelta - what's new for perl v5.6.0
This document describes differences between the 5.005 release and this one.
Perl 5.005_63 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.
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.
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''.
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 unintialized 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.
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.
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.
NOTE: The Compiler suite remains highly experimental. The
generated code may not be correct, even 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 someting
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 compatability.
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 [email protected] 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 fastervalues() 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.
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 accomodate 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 neccessity generated as warnings followed by eventual termination of the program. This enabled more such errors to be reported in a single run, rather than causing a hard stop at the first error that was encountered.
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.
See 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
spearate 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.
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.
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.
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) operate on
aliases to values, not copiesvalues() and hashes in a list context
return the actual values in the hash, instead of copies (as they used to in
earlier versions). Typical idioms for using these constructs copy the returned
values, but this can make a significant difference when creating references to
the returned values. Keys in the hash are still returned as copies when
iterating on a hash.
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.
If your platform is either natively 64-bit or if Perl has been configured to
used 64-bit integers, i.e., $Config{ivsize} is 8, there may be a potential
incompatibility in the behavior of bitwise numeric operators (& | ^ ~
<< >>). These operators used to strictly operate on the lower 32
bits of integers in previous versions, but now operate over the entire native
integral width. In particular, note that unary ~ will produce
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.
See Bit operators support full native integer width.
As described in Improved security features, there may be more sources of taint in a Perl program.
To avoid these new tainting behaviors, you can build Perl with the Configure
option -Accflags=-DINCOMPLETE_TAINTS. Beware that the 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.
The subtests 19 and 20 of lib/thr5005.t test are known to fail due to fundamental problems in the 5.005 threading implementation. These are not new failures--Perl 5.005_0x has the same bugs, but didn't have these tests.
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 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).
In NEXTSTEP 3.3p2 the implementation of the
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.
If compiled with gcc 2.95 the lib/sdbm test will fail (dump core). The cure is to use the vendor cc, it comes with the operating system and produces good code.
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.
Windows 2000 is known to fail test 22 in lib/open3.t (cause unknown at this time). That test passes under Windows NT.
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 })
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/perl/, 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 [email protected] 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 <[email protected]>, with many contributions from The Perl Porters.
Send omissions or corrections to <[email protected]>.