Perl has never guaranteed any ordering of the hash keys, and the ordering has already changed several times during the lifetime of Perl 5. Also, the ordering of hash keys has always been, and continues to be, affected by the insertion order.
The added randomness may affect applications.
One possible scenario is when output of an application has included hash data. For example, if you have used the Data::Dumper module to dump data into different files, and then compared the files to see whether the data has changed, now you will have false positives since the order in which hashes are dumped will vary. In general the cure is to sort the keys (or the values); in particular for Data::Dumper to use the "Sortkeys" option. If some particular order is really important, use tied hashes: for example the Tie::IxHash module which by default preserves the order in which the hash elements were added.
More subtle problem is reliance on the order of ``global destruction''. That is what happens at the end of execution: Perl destroys all data structures, including user data. If your destructors (the DESTROY subroutines) have assumed any particular ordering to the global destruction, there might be problems ahead. For example, in a destructor of one object you cannot assume that objects of any other class are still available, unless you hold a reference to them. If the environment variable PERL_DESTRUCT_LEVEL is set to a non-zero value, or if Perl is exiting a spawned thread, it will also destruct the ordinary references and the symbol tables that are no longer in use. You can't call a class method or an ordinary function on a class that has been collected that way.
The hash randomisation is certain to reveal hidden assumptions about some particular ordering of hash elements, and outright bugs: it revealed a few bugs in the Perl core and core modules.
To disable the hash randomisation in runtime, set the environment variable PERL_HASH_SEED to 0 (zero) before running Perl (for more information see ``PERL_HASH_SEED'' in perlrun), or to disable the feature completely in compile time, compile with "-DNO_HASH_SEED" (see INSTALL).
See ``Algorithmic Complexity Attacks'' in perlsec for the original rationale behind this change.
%h = ( v65 => 42 );
has meant since Perl 5.6.0
%h = ( 'A' => 42 );
(at least in platforms of ASCII progeny) Perl 5.8.1 restored the more natural interpretation
%h = ( 'v65' => 42 );
The multi-number v-strings like v65.66 and 65.66.67 still continue to be v-strings in Perl 5.8.
For the new life of this switch, see ``UTF-8 no longer default under UTF-8 locales'', and ``-C'' in perlrun.
$a // $b
is merely equivalent to
defined $a ? $a : $b
and
$c //= $d;
can be used instead of
$c = $d unless defined $c;
This operator has the same precedence and associativity as "||". It has a low-precedence counterpart, "err", which has the same precedence and associativity as "or". Special care has been taken to ensure that those operators Do What You Mean while not breaking old code, but some edge cases involving the empty regular expression may now parse differently. See perlop for details.
For example, if you had "en_US.UTF-8" as your locale, your STDIN and STDOUT were automatically ``UTF-8'', in other words an implicit binmode(..., ``:utf8'') was made. This meant that trying to print, say, chr(0xff), ended up printing the bytes 0xc3 0xbf. Hardly what you had in mind unless you were aware of this feature of Perl 5.8.0. The problem is that the vast majority of people weren't: for example in RedHat releases 8 and 9 the default locale setting is UTF-8, so all RedHat users got UTF-8 filehandles, whether they wanted it or not. The pain was intensified by the Unicode implementation of Perl 5.8.0 (still) having nasty bugs, especially related to the use of s/// and tr///. (Bugs that have been fixed in 5.8.1)
Therefore a decision was made to backtrack the feature and change it from implicit silent default to explicit conscious option. The new Perl command line option "-C" and its counterpart environment variable PERL_UNICODE can now be used to control how Perl and Unicode interact at interfaces like I/O and for example the command line arguments. See ``-C'' in perlrun and ``PERL_UNICODE'' in perlrun for more information.
However, the new safer model has its problems too. Because now an opcode, a basic unit of Perl execution, is never interrupted but instead let to run to completion, certain operations that can take a long time now really do take a long time. For example, certain network operations have their own blocking and timeout mechanisms, and being able to interrupt them immediately would be nice.
Therefore perl 5.8.1 introduced a ``backdoor'' to restore the pre-5.8.0 (pre-5.7.3, really) signal behaviour. Just set the environment variable PERL_SIGNALS to "unsafe", and the old immediate (and unsafe) signal handling behaviour returns. See ``PERL_SIGNALS'' in perlrun and ``Deferred Signals (Safe Signals)'' in perlipc.
In completely unrelated news, you can now use safe signals with POSIX::SigAction. See ``POSIX::SigAction'' in POSIX.
local ${$x}
local @{$x}
local %{$x}
now do localise variables, given that the $x is a valid variable name.
"map" in void context is no longer expensive. "map" is now context aware, and will not construct a list if called in void context.
If a socket gets closed by the server while printing to it, the client now gets a SIGPIPE. While this new feature was not planned, it fell naturally out of PerlIO changes, and is to be considered an accidental feature.
PerlIO::get_layers(FH) returns the names of the PerlIO layers active on a filehandle.
PerlIO::via layers can now have an optional UTF8 method to indicate whether the layer wants to ``auto-:utf8'' the stream.
utf8::is_utf8() has been added as a quick way to test whether a scalar is encoded internally in UTF-8 (Unicode).
If a filehandle has been marked as to have an encoding, unmappable characters are detected already during input, not later (when the corrupted data is being used).
The ISO 8859-6 conversion table has been corrected (the 0x30..0x39 erroneously mapped to U+0660..U+0669, instead of U+0030..U+0039). The GSM 03.38 conversion did not handle escape sequences correctly. The UTF-7 encoding has been added (making Encode feature-complete with Unicode::String).
Some new features were added, e.g. the broot() method, you can now pass parameters to config() to change some settings at runtime, and it is now possible to trap the creation of NaN and infinity.
As usual, some optimizations took place and made the math overall a tad faster. In some cases, quite a lot faster, actually. Especially alternative libraries like Math::BigInt::GMP benefit from this. In addition, a lot of the quite clunky routines like fsqrt() and flog() are now much much faster.
use strict qw(@ISA);
@ISA = qw(Foo);
This however (probably) raised the false expectation that the strict refs, vars and subs were being enforced (and that @ISA was somehow ``declared''). But the strict refs, vars, and subs are not enforced when using this false idiom.
Starting from Perl 5.8.1, the above will cause an error to be raised. This may cause programs which used to execute seemingly correctly without warnings and errors to fail when run under 5.8.1. This happens because
use strict qw(@ISA);
will now fail with the error:
Unknown 'strict' tag(s) '@ISA'
The remedy to this problem is to replace this code with the correct idiom:
use strict;
use vars qw(@ISA);
@ISA = qw(Foo);
The Perl debugger (lib/perl5db.pl) has now been extensively documented and bugs found while documenting have been fixed.
"perldoc" has been rewritten from scratch to be more robust and feature rich.
"perlcc -B" works now at least somewhat better, while "perlcc -c" is rather more broken. (The Perl compiler suite as a whole continues to be experimental.)
perl58delta and perl581delta have been added: these are the perldeltas of 5.8.0 and 5.8.1, detailing the differences respectively between 5.6.0 and 5.8.0, and between 5.8.0 and 5.8.1.
perlartistic has been added: it is the Artistic License in pod format, making it easier for modules to refer to it.
perlcheat has been added: it is a Perl cheat sheet.
perlgpl has been added: it is the GNU General Public License in pod format, making it easier for modules to refer to it.
perlmacosx has been added to tell about the installation and use of Perl in Mac OS X.
perlos400 has been added to tell about the installation and use of Perl in OS/400 PASE.
perlreref has been added: it is a regular expressions quick reference.
One can now specify installation directories for site and vendor man and HTML pages, and site and vendor scripts. See INSTALL.
One can now specify a destination directory for Perl installation by specifying the DESTDIR variable for "make install". (This feature is slightly different from the previous "Configure -Dinstallprefix=...".) See INSTALL.
gcc versions 3.x introduced a new warning that caused a lot of noise during Perl compilation: "gcc -Ialreadyknowndirectory (warning: changing search order)". This warning has now been avoided by Configure weeding out such directories before the compilation.
One can now build subsets of Perl core modules by using the Configure flags "-Dnoextensions=..." and "-Donlyextensions=...", see INSTALL.
In newer FreeBSD releases Perl 5.8.0 compilation failed because of trying to use malloc.h, which in FreeBSD is just a dummy file, and a fatal error to even try to use. Now malloc.h is not used.
Perl is now known to build also in Hitachi HI-UXMPP.
Perl is now known to build again in LynxOS.
Mac OS X now installs with Perl version number embedded in installation directory names for easier upgrading of user-compiled Perl, and the installation directories in general are more standard. In other words, the default installation no longer breaks the Apple-provided Perl. On the other hand, with "Configure -Dprefix=/usr" you can now really replace the Apple-supplied Perl (please be careful).
Mac OS X now builds Perl statically by default. This change was done mainly for faster startup times. The Apple-provided Perl is still dynamically linked and shared, and you can enable the sharedness for your own Perl builds by "Configure -Duseshrplib".
Perl has been ported to IBM's OS/400 PASE environment. The best way to build a Perl for PASE is to use an AIX host as a cross-compilation environment. See README.os400.
Yet another cross-compilation option has been added: now Perl builds on OpenZaurus, an Linux distribution based on Mandrake + Embedix for the Sharp Zaurus PDA. See the Cross/README file.
Tru64 when using gcc 3 drops the optimisation for toke.c to "-O2" because of gigantic memory use with the default "-O3".
Tru64 can now build Perl with the newer Berkeley DBs.
Building Perl on WinCE has been much enhanced, see README.ce and README.perlce.
binmode(SOCKET, ``:utf8'') only worked on the input side, not on the output side of the socket. Now it works both ways.
For threaded Perls certain system database functions like getpwent() and getgrent() now grow their result buffer dynamically, instead of failing. This means that at sites with lots of users and groups the functions no longer fail by returning only partial results.
Perl 5.8.0 had accidentally broken the capability for users to define their own uppercase<->lowercase Unicode mappings (as advertised by the Camel). This feature has been fixed and is also documented better.
In 5.8.0 this
$some_unicode .= <FH>;
didn't work correctly but instead corrupted the data. This has now been fixed.
Tied methods like FETCH etc. may now safely access tied values, i.e. resulting in a recursive call to FETCH etc. Remember to break the recursion, though.
At startup Perl blocks the SIGFPE signal away since there isn't much Perl can do about it. Previously this blocking was in effect also for programs executed from within Perl. Now Perl restores the original SIGFPE handling routine, whatever it was, before running external programs.
Linenumbers in Perl scripts may now be greater than 65536, or 2**16. (Perl scripts have always been able to be larger than that, it's just that the linenumber for reported errors and warnings have ``wrapped around''.) While scripts that large usually indicate a need to rethink your code a bit, such Perl scripts do exist, for example as results from generated code. Now linenumbers can go all the way to 4294967296, or 2**32.
HP-UX
VMS
Win32
A thread exited while %d other threads were still running
was misleading because the ``other'' included also the thread giving the warning.
Invalid [] range "%s" in transliteration operator
was simply wrong because there are no ``[] ranges'' in tr///.
$x & $y == 0
tests whether the bitwise AND of $x and $y is zero, you will like this warning.
The embedding examples of perlembed have been reviewed to be up to date and consistent: for example, the correct use of PERL_SYS_INIT3() and PERL_SYS_TERM().
Extensive reworking of the pad code (the code responsible for lexical variables) has been conducted by Dave Mitchell.
Extensive work on the v-strings by John Peacock.
UTF-8 length and position cache: to speed up the handling of Unicode (UTF-8) scalars, a cache was introduced. Potential problems exist if an extension bypasses the official APIs and directly modifies the PV of an SV: the UTF-8 cache does not get cleared as it should.
APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv, sv_setsv, are again available.
Certain Perl core C APIs like cxinc and regatom are no longer available at all to code outside the Perl core of the Perl core extensions. This is intentional. They never should have been available with the shorter names, and if you application depends on them, you should (be ashamed and) contact perl5-porters to discuss what are the proper APIs.
Certain Perl core C APIs like "Perl_list" are no longer available without their "Perl_" prefix. If your XS module stops working because some functions cannot be found, in many cases a simple fix is to add the "Perl_" prefix to the function and the thread context "aTHX_" as the first argument of the function call. This is also how it should always have been done: letting the Perl_-less forms to leak from the core was an accident. For cleaner embedding you can also force this for all APIs by defining at compile time the cpp define PERL_NO_SHORT_NAMES.
Perl_save_bool() has been added.
Regexp objects (those created with "qr") now have S-magic rather than R-magic. This fixed regexps of the form /...(??{...;$x})/ to no longer ignore changes made to $x. The S-magic avoids dropping the caching optimization and making (??{...}) constructs obscenely slow (and consequently useless). See also ``Magic Variables'' in perlguts. Regexp::Copy was affected by this change.
The Perl internal debugging macros DEBUG() and DEB() have been renamed to PERL_DEBUG() and PERL_DEB() to avoid namespace conflicts.
"-DL" removed (the leaktest had been broken and unsupported for years, use alternative debugging mallocs or tools like valgrind and Purify).
Verbose modifier "v" added for "-DXv" and "-Dsv", see perlrun.
Many of the rarer platforms that worked 100% or pretty close to it with perl 5.8.0 have been left a little bit untended since their maintainers have been otherwise busy lately, and therefore there will be more failures on those platforms. Such platforms include Mac OS Classic, IBM z/OS (and other EBCDIC platforms), and NetWare. The most common Perl platforms (Unix and Unix-like, Microsoft platforms, and VMS) have large enough testing and expert population that they are doing well.
if (%tied_hash) { ... }
The current nonsensical behaviour is always to return false, regardless of whether the hash is empty or has elements.
The root cause is that there is no interface for the implementors of tied hashes to implement the behaviour of a hash in scalar context.
Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a) "CYGWIN_NT-5.0 ... 1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ..." a 100% ``make test'' was achieved with "Configure -des -Duseithreads".
cc: "/usr/include/sys/socket.h", line 504: warning 562:
Redeclaration of "sendfile" with a different storage class specifier:
"sendfile" will have internal linkage.
cc: "/usr/include/sys/socket.h", line 505: warning 562:
Redeclaration of "sendpath" with a different storage class specifier:
"sendpath" will have internal linkage.
The warnings show up both during the build of Perl and during certain lib/ExtUtils tests that invoke the C compiler. The warning, however, is not serious and can be ignored.
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. You can browse and search the Perl 5 bugs at http://bugs.perl.org/.
The INSTALL file for how to build Perl.
The README file for general stuff.
The Artistic and Copying files for copyright information.