PERL581DELTA(1) Perl Programmers Reference Guide PERL581DELTA(1)

PERL581DELTA(1) Perl Programmers Reference Guide PERL581DELTA(1) #

PERL581DELTA(1) Perl Programmers Reference Guide PERL581DELTA(1)

NNAAMMEE #

 perl581delta - what is new for perl v5.8.1

DDEESSCCRRIIPPTTIIOONN #

 This document describes differences between the 5.8.0 release and the
 5.8.1 release.

 If you are upgrading from an earlier release such as 5.6.1, first read
 the perl58delta, which describes differences between 5.6.0 and 5.8.0.

 In case you are wondering about 5.6.1, it was bug-fix-wise rather
 identical to the development release 5.7.1.  Confused?  This timeline
 hopefully helps a bit: it lists the new major releases, their maintenance
 releases, and the development releases.

           New     Maintenance  Development

           5.6.0                             2000-Mar-22
                                5.7.0        2000-Sep-02
                   5.6.1                     2001-Apr-08
                                5.7.1        2001-Apr-09
                                5.7.2        2001-Jul-13
                                5.7.3        2002-Mar-05
           5.8.0                             2002-Jul-18
                   5.8.1                     2003-Sep-25

IInnccoommppaattiibbllee CChhaannggeess HHaasshh RRaannddoommiissaattiioonn Mainly due to security reasons, the “random ordering” of hashes has been made even more random. Previously while the order of hash elements from kkeeyyss(()), vvaalluueess(()), and eeaacchh(()) was essentially random, it was still repeatable. Now, however, the order varies between different runs of Perl.

 PPeerrll hhaass nneevveerr gguuaarraanntteeeedd aannyy oorrddeerriinngg ooff tthhee hhaasshh kkeeyyss, 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 _I_N_S_T_A_L_L).

 See "Algorithmic Complexity Attacks" in perlsec for the original
 rationale behind this change.

UUTTFF--88 OOnn FFiilleehhaannddlleess NNoo LLoonnggeerr AAccttiivvaatteedd BByy LLooccaallee In Perl 5.8.0 all filehandles, including the standard filehandles, were implicitly set to be in Unicode UTF-8 if the locale settings indicated the use of UTF-8. This feature caused too many problems, so the feature was turned off and redesigned: see “Core Enhancements”.

SSiinnggllee--nnuummbbeerr vv--ssttrriinnggss aarree nnoo lloonnggeerr vv--ssttrriinnggss bbeeffoorree “”==>>“” The version strings or v-strings (see “Version Strings” in perldata) feature introduced in Perl 5.6.0 has been a source of some confusion– especially when the user did not want to use it, but Perl thought it knew better. Especially troublesome has been the feature that before a “=>” a version string (a “v” followed by digits) has been interpreted as a v-string instead of a string literal. In other words:

         %h = ( v65 => 42 );

 has meant since Perl 5.6.0

         %h = ( 'A' => 42 );

 (at least in platforms of ASCII progeny)  Perl 5.8.1 restores 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.

((WWiinn3322)) TThhee --CC SSwwiittcchh HHaass BBeeeenn RReeppuurrppoosseedd The -C switch has changed in an incompatible way. The old semantics of this switch only made sense in Win32 and only in the “use utf8” universe in 5.6.x releases, and do not make sense for the Unicode implementation in 5.8.0. Since this switch could not have been used by anyone, it has been repurposed. The behavior that this switch enabled in 5.6.x releases may be supported in a transparent, data-dependent fashion in a future release.

 For the new life of this switch, see "UTF-8 no longer default under UTF-8
 locales", and "-C" in perlrun.

((WWiinn3322)) TThhee //dd SSwwiittcchh OOff ccmmdd..eexxee Perl 5.8.1 uses the /d switch when running the cmd.exe shell internally for ssyysstteemm(()), backticks, and when opening pipes to external programs. The extra switch disables the execution of AutoRun commands from the registry, which is generally considered undesirable when running external programs. If you wish to retain compatibility with the older behavior, set PERL5SHELL in your environment to “cmd /x/c”.

CCoorree EEnnhhaanncceemmeennttss UUTTFF--88 nnoo lloonnggeerr ddeeffaauulltt uunnddeerr UUTTFF--88 llooccaalleess In Perl 5.8.0 many Unicode features were introduced. One of them was found to be of more nuisance than benefit: the automagic (and silent) “UTF-8-ification” of filehandles, including the standard filehandles, if the user’s locale settings indicated use of UTF-8.

 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,
 cchhrr(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 ddeeffaauulltt 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.

UUnnssaaffee ssiiggnnaallss aaggaaiinn aavvaaiillaabbllee In Perl 5.8.0 the so-called “safe signals” were introduced. This means that Perl no longer handles signals immediately but instead “between opcodes”, when it is safe to do so. The earlier immediate handling easily could corrupt the internal state of Perl, resulting in mysterious crashes.

 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 introduces 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.

TTiieedd AArrrraayyss wwiitthh NNeeggaattiivvee AArrrraayy IInnddiicceess Formerly, the indices passed to “FETCH”, “STORE”, “EXISTS”, and “DELETE” methods in tied array class were always non-negative. If the actual argument was negative, Perl would call FETCHSIZE implicitly and add the result to the index before passing the result to the tied array method. This behaviour is now optional. If the tied array class contains a package variable named $NEGATIVE_INDICES which is set to a true value, negative values will be passed to “FETCH”, “STORE”, “EXISTS”, and “DELETE” unchanged.

llooccaall $${{$$xx}} The syntaxes

         local ${$x}
         local @{$x}
         local %{$x}

 now do localise variables, given that the $x is a valid variable name.

UUnniiccooddee CChhaarraacctteerr DDaattaabbaassee 44..00..00 The copy of the Unicode Character Database included in Perl 5.8 has been updated to 4.0.0 from 3.2.0. This means for example that the Unicode character properties are as in Unicode 4.0.0.

DDeepprreeccaattiioonn WWaarrnniinnggss There is one new feature deprecation. Perl 5.8.0 forgot to add some deprecation warnings, these warnings have now been added. Finally, a reminder of an impending feature removal.

 _(_R_e_m_i_n_d_e_r_) _P_s_e_u_d_o_-_h_a_s_h_e_s _a_r_e _d_e_p_r_e_c_a_t_e_d _(_r_e_a_l_l_y_)

 Pseudo-hashes were deprecated in Perl 5.8.0 and will be removed in Perl
 5.10.0, see perl58delta for details.  Each attempt to access pseudo-
 hashes will trigger the warning "Pseudo-hashes are deprecated".  If you
 really want to continue using pseudo-hashes but not to see the
 deprecation warnings, use:

     no warnings 'deprecated';

 Or you can continue to use the fields pragma, but please don't expect the
 data structures to be pseudohashes any more.

 _(_R_e_m_i_n_d_e_r_) _5_._0_0_5_-_s_t_y_l_e _t_h_r_e_a_d_s _a_r_e _d_e_p_r_e_c_a_t_e_d _(_r_e_a_l_l_y_)

 5.005-style threads (activated by "use Thread;") were deprecated in Perl
 5.8.0 and will be removed after Perl 5.8, see perl58delta for details.
 Each 5.005-style thread creation will trigger the warning "5.005 threads
 are deprecated".  If you really want to continue using the 5.005 threads
 but not to see the deprecation warnings, use:

     no warnings 'deprecated';

 _(_R_e_m_i_n_d_e_r_) _T_h_e _$_* _v_a_r_i_a_b_l_e _i_s _d_e_p_r_e_c_a_t_e_d _(_r_e_a_l_l_y_)

 The $* variable controlling multi-line matching has been deprecated and
 will be removed after 5.8.  The variable has been deprecated for a long
 time, and a deprecation warning "Use of $* is deprecated" is given, now
 the variable will just finally be removed.  The functionality has been
 supplanted by the "/s" and "/m" modifiers on pattern matching.  If you
 really want to continue using the $*-variable but not to see the
 deprecation warnings, use:

     no warnings 'deprecated';

MMiisscceellllaanneeoouuss EEnnhhaanncceemmeennttss “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.

 uuttff88::::iiss__uuttff88(()) has been added as a quick way to test whether a scalar is
 encoded internally in UTF-8 (Unicode).

MMoodduulleess aanndd PPrraaggmmaattaa UUppddaatteedd MMoodduulleess AAnndd PPrraaggmmaattaa The following modules and pragmata have been updated since Perl 5.8.0:

 base
 B::Bytecode
     In much better shape than it used to be.  Still far from perfect, but
     maybe worth a try.

 B::Concise
 B::Deparse
 Benchmark
     An optional feature, ":hireswallclock", now allows for high
     resolution wall clock times (uses Time::HiRes).

 ByteLoader
     See B::Bytecode.

 bytes
     Now has bytes::substr.

CGI #

 charnames
     One can now have custom character name aliases.

CPAN #

     There is now a simple command line frontend to the CPAN.pm module
     called _c_p_a_n.

 Data::Dumper
     A new option, Pair, allows choosing the separator between hash keys
     and values.

 DB_File
 Devel::PPPort
 Digest::MD5
 Encode
     Significant updates on the encoding pragma functionality (tr/// and
     the DATA filehandle, formats).

     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).

 fields
 libnet
 Math::BigInt
     A lot of bugs have been fixed since v1.60, the version included in
     Perl v5.8.0. Especially noteworthy are the bug in Calc that caused
     div and mod to fail for some large values, and the fixes to the
     handling of bad inputs.

     Some new features were added, e.g. the bbrroooott(()) method, you can now
     pass parameters to ccoonnffiigg(()) 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 ffssqqrrtt(()) and fflloogg(())
     are now much much faster.

 MIME::Base64

NEXT #

     Diamond inheritance now works.

 Net::Ping
 PerlIO::scalar
     Reading from non-string scalars (like the special variables, see
     perlvar) now works.

 podlators
 Pod::LaTeX
 PodParsers
 Pod::Perldoc
     Complete rewrite.  As a side-effect, no longer refuses to startup
     when run by root.

 Scalar::Util
     New utilities: refaddr, isvstring, looks_like_number, set_prototype.

 Storable
     Can now store code references (via B::Deparse, so not foolproof).

 strict
     Earlier versions of the strict pragma did not check the parameters
     implicitly passed to its "import" (use) and "unimport" (no) routine.
     This caused the false idiom such as:

             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 nnoott enforced
     when using this false idiom.

     Starting from Perl 5.8.1, the above wwiillll 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);

 Term::ANSIcolor
 Test::Harness
     Now much more picky about extra or missing output from test scripts.

 Test::More
 Test::Simple
 Text::Balanced
 Time::HiRes
     Use of nnaannoosslleeeepp(()), if available, allows mixing subsecond sleeps with
     alarms.

 threads
     Several fixes, for example for jjooiinn(()) problems and memory leaks.  In
     some platforms (like Linux) that use glibc the minimum memory
     footprint of one ithread has been reduced by several hundred
     kilobytes.

 threads::shared
     Many memory leaks have been fixed.

 Unicode::Collate
 Unicode::Normalize
 Win32::GetFolderPath
 Win32::GetOSVersion
     Now returns extra information.

UUttiilliittyy CChhaannggeess The “h2xs” utility now produces a more modern layout: _F_o_o_-_B_a_r_/_l_i_b_/_F_o_o_/_B_a_r_._p_m instead of _F_o_o_/_B_a_r_/_B_a_r_._p_m. Also, the boilerplate test is now called _t_/_F_o_o_-_B_a_r_._t instead of _t_/_1_._t.

 The Perl debugger (_l_i_b_/_p_e_r_l_5_d_b_._p_l) 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.)

NNeeww DDooccuummeennttaattiioonn perl573delta has been added to list the differences between the (now quite obsolete) development releases 5.7.2 and 5.7.3.

 perl58delta has been added: it is the perldelta of 5.8.0, detailing the
 differences between 5.6.0 and 5.8.0.

 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.

IInnssttaallllaattiioonn aanndd CCoonnffiigguurraattiioonn IImmpprroovveemmeennttss The Unix standard Perl location, _/_u_s_r_/_b_i_n_/_p_e_r_l, is no longer overwritten by default if it exists. This change was very prudent because so many Unix vendors already provide a _/_u_s_r_/_b_i_n_/_p_e_r_l, but simultaneously many system utilities may depend on that exact version of Perl, so better not to overwrite it.

 One can now specify installation directories for site and vendor man and
 HTML pages, and site and vendor scripts.  See _I_N_S_T_A_L_L.

 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 _I_N_S_T_A_L_L.

 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 _I_N_S_T_A_L_L.

PPllaattffoorrmm--ssppeecciiffiicc eennhhaanncceemmeennttss In Cygwin Perl can now be built with threads (“Configure -Duseithreads”). This works with both Cygwin 1.3.22 and Cygwin 1.5.3.

 In newer FreeBSD releases Perl 5.8.0 compilation failed because of trying
 to use _m_a_l_l_o_c_._h, which in FreeBSD is just a dummy file, and a fatal error
 to even try to use.  Now _m_a_l_l_o_c_._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 (pplleeaassee bbee ccaarreeffuull).

 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, a 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 _t_o_k_e_._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 _R_E_A_D_M_E_._c_e and
 _R_E_A_D_M_E_._p_e_r_l_c_e.

SSeelleecctteedd BBuugg FFiixxeess CClloossuurreess,, eevvaall aanndd lleexxiiccaallss There have been many fixes in the area of anonymous subs, lexicals and closures. Although this means that Perl is now more “correct”, it is possible that some existing code will break that happens to rely on the faulty behaviour. In practice this is unlikely unless your code contains a very complex nesting of anonymous subs, evals and lexicals.

GGeenneerriicc ffiixxeess If an input filehandle is marked “:utf8” and Perl sees illegal UTF-8 coming in when doing “”, if warnings are enabled a warning is immediately given - instead of being silent about it and Perl being unhappy about the broken data later. (The “:encoding(utf8)” layer also works the same way.)

 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 ggeettppwweenntt(()) and
 ggeettggrreenntt(()) 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.

PPllaattffoorrmm--ssppeecciiffiicc ffiixxeess Linux

 •   Setting $0 works again (with certain limitations that Perl cannot do
     much about: see "$0" in perlvar)

HP-UX #

 •   Setting $0 now works.

VMS #

 •   Configuration now tests for the presence of "poll()", and IO::Poll
     now uses the vendor-supplied function if detected.

 •   A rare access violation at Perl start-up could occur if the Perl
     image was installed with privileges or if there was an identifier
     with the subsystem attribute set in the process's rightslist.  Either
     of these circumstances triggered tainting code that contained a
     pointer bug.  The faulty pointer arithmetic has been fixed.

 •   The length limit on values (not keys) in the %ENV hash has been
     raised from 255 bytes to 32640 bytes (except when the PERL_ENV_TABLES
     setting overrides the default use of logical names for %ENV).  If it
     is necessary to access these long values from outside Perl, be aware
     that they are implemented using search list logical names that store
     the value in pieces, each 255-byte piece (up to 128 of them) being an
     element in the search list. When doing a lookup in %ENV from within
     Perl, the elements are combined into a single value.  The existing
     VMS-specific ability to access individual elements of a search list
     logical name via the $ENV{'foo;N'} syntax (where N is the search list
     index) is unimpaired.

 •   The piping implementation now uses local rather than global DCL
     symbols for inter-process communication.

 •   File::Find could become confused when navigating to a relative
     directory whose name collided with a logical name.  This problem has
     been corrected by adding directory syntax to relative path names,
     thus preventing logical name translation.

 Win32

 •   A memory leak in the ffoorrkk(()) emulation has been fixed.

 •   The return value of the iiooccttll(()) built-in function was accidentally
     broken in 5.8.0.  This has been corrected.

 •   The internal message loop executed by perl during blocking operations
     sometimes interfered with messages that were external to Perl.  This
     often resulted in blocking operations terminating prematurely or
     returning incorrect results, when Perl was executing under
     environments that could generate Windows messages.  This has been
     corrected.

 •   Pipes and sockets are now automatically in binary mode.

 •   The four-argument form of sseelleecctt(()) did not preserve $! (errno)
     properly when there were errors in the underlying call.  This is now
     fixed.

 •   The "CR CR LF" problem of has been fixed, binmode(FH, ":crlf") is now
     effectively a no-op.

NNeeww oorr CChhaannggeedd DDiiaaggnnoossttiiccss All the warnings related to ppaacckk(()) and uunnppaacckk(()) were made more informative and consistent.

CChhaannggeedd “"AA tthhrreeaadd eexxiitteedd wwhhiillee %%dd tthhrreeaaddss wweerree rruunnnniinngg"” The old version

     A thread exited while %d other threads were still running

 was misleading because the "other" included also the thread giving the
 warning.

RReemmoovveedd “"AAtttteemmpptt ttoo cclleeaarr aa rreessttrriicctteedd hhaasshh"” It is not illegal to clear a restricted hash, so the warning was removed.

NNeeww “"IIlllleeggaall ddeeccllaarraattiioonn ooff aannoonnyymmoouuss ssuubbrroouuttiinnee"” You must specify the block of code for “sub”.

CChhaannggeedd “"IInnvvaalliidd rraannggee “”%%ss"” iinn ttrraannsslliitteerraattiioonn ooppeerraattoorr"" The old version

     Invalid [] range "%s" in transliteration operator

 was simply wrong because there are no "[] ranges" in tr///.

NNeeww “"MMiissssiinngg ccoonnttrrooll cchhaarr nnaammee iinn \\cc"” Self-explanatory.

NNeeww “"NNeewwlliinnee iinn lleefftt--jjuussttiiffiieedd ssttrriinngg ffoorr %%ss"” The padding spaces would appear after the newline, which is probably not what you had in mind.

NNeeww “"PPoossssiibbllee pprreecceeddeennccee pprroobblleemm oonn bbiittwwiissee %%cc ooppeerraattoorr"” If you think this

     $x & $y == 0

 tests whether the bitwise AND of $x and $y is zero, you will like this
 warning.

NNeeww “"PPsseeuuddoo--hhaasshheess aarree ddeepprreeccaatteedd"” This warning should have been already in 5.8.0, since they are.

NNeeww “"rreeaadd(()) oonn %%ss ffiilleehhaannddllee %%ss"” You cannot rreeaadd(()) (or ssyyssrreeaadd(())) from a closed or unopened filehandle.

NNeeww “"55..000055 tthhrreeaaddss aarree ddeepprreeccaatteedd"” This warning should have been already in 5.8.0, since they are.

NNeeww “"TTiieedd vvaarriiaabbllee ffrreeeedd wwhhiillee ssttiillll iinn uussee"” Something pulled the plug on a live tied variable, Perl plays safe by bailing out.

NNeeww “"TToo%%ss:: iilllleeggaall mmaappppiinngg ‘’%%ss’’“” An illegal user-defined Unicode casemapping was specified.

NNeeww “"UUssee ooff ffrreeeedd vvaalluuee iinn iitteerraattiioonn"” Something modified the values being iterated over. This is not good.

CChhaannggeedd IInntteerrnnaallss These news matter to you only if you either write XS code or like to know about or hack Perl internals (using Devel::Peek or any of the “B::” modules counts), or like to run Perl with the “-D” option.

 The embedding examples of perlembed have been reviewed to be up to date
 and consistent: for example, the correct use of PPEERRLL__SSYYSS__IINNIITT33(()) and

PPEERRLL__SSYYSS__TTEERRMM(()). #

 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.

 PPeerrll__ssaavvee__bbooooll(()) 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 DDEEBBUUGG(()) and DDEEBB(()) have been renamed to
 PPEERRLL__DDEEBBUUGG(()) and PPEERRLL__DDEEBB(()) 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.

NNeeww TTeessttss In Perl 5.8.0 there were about 69000 separate tests in about 700 test files, in Perl 5.8.1 there are about 77000 separate tests in about 780 test files. The exact numbers depend on the Perl configuration and on the operating system platform.

KKnnoowwnn PPrroobblleemmss The hash randomisation mentioned in “Incompatible Changes” is definitely problematic: it will wake dormant bugs and shake out bad assumptions.

 If you want to use mod_perl 2.x with Perl 5.8.1, you will need
 mod_perl-1.99_10 or higher.  Earlier versions of mod_perl 2.x do not work
 with the randomised hashes.  (mod_perl 1.x works fine.)  You will also
 need Apache::Test 1.04 or higher.

 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.

TTiieedd hhaasshheess iinn ssccaallaarr ccoonntteexxtt Tied hashes do not currently return anything useful in scalar context, for example when used as boolean tests:

         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.

NNeett::::PPiinngg 445500__sseerrvviiccee aanndd 551100__ppiinngg__uuddpp ffaaiilluurreess The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the subtest 2 of lib/Net/Ping/t/510_ping_udp.t might fail if you have an unusual networking setup. For example in the latter case the test is trying to send a UDP ping to the IP address 127.0.0.1.

BB::::CC #

 The C-generating compiler backend B::C (the frontend being "perlcc -c")
 is even more broken than it used to be because of the extensive lexical
 variable changes.  (The good news is that B::Bytecode and ByteLoader are
 better than they used to be.)

PPllaattffoorrmm SSppeecciiffiicc PPrroobblleemmss EEBBCCDDIICC PPllaattffoorrmmss IBM z/OS and other EBCDIC platforms continue to be problematic regarding Unicode support. Many Unicode tests are skipped when they really should be fixed.

CCyyggwwiinn 11..55 pprroobblleemmss In Cygwin 1.5 the _i_o_/_t_e_l_l and _o_p_/_s_y_s_i_o tests have failures for some yet unknown reason. In 1.5.5 the threads tests stress_cv, stress_re, and stress_string are failing unless the environment variable PERLIO is set to “perlio” (which makes also the io/tell failure go away).

 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".

HHPP--UUXX:: HHPP cccc wwaarrnniinnggss aabboouutt sseennddffiillee aanndd sseennddppaatthh With certain HP C compiler releases (e.g. B.11.11.02) you will get many warnings like this (lines wrapped for easier reading):

   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.

IIRRIIXX:: tt//uunnii//ttrr__77jjiiss..tt ffaallsseellyy ffaaiilliinngg The test t/uni/tr_7jis.t is known to report failure under ‘make test’ or the test harness with certain releases of IRIX (at least IRIX 6.5 and MIPSpro Compilers Version 7.3.1.1m), but if run manually the test fully passes.

MMaacc OOSS XX:: nnoo uusseemmyymmaalllloocc The Perl malloc ("-Dusemymalloc”) does not work at all in Mac OS X. This is not that serious, though, since the native malloc works just fine.

TTrruu6644:: NNoo tthhrreeaaddeedd bbuuiillddss wwiitthh GGNNUU cccc ((ggcccc)) In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used to compile a threaded Perl (-Duseithreads) because the system “<pthread.h>” file doesn’t know about gcc.

WWiinn3322:: ssyyssooppeenn,, ssyyssrreeaadd,, ssyysswwrriittee As of the 5.8.0 release, ssyyssooppeenn(())/ssyyssrreeaadd(())/ssyysswwrriittee(()) do not behave like they used to in 5.6.1 and earlier with respect to “text” mode. These built-ins now always operate in “binary” mode (even if ssyyssooppeenn(()) was passed the O_TEXT flag, or if bbiinnmmooddee(()) was used on the file handle). Note that this issue should only make a difference for disk files, as sockets and pipes have always been in “binary” mode in the Windows port. As this behavior is currently considered a bug, compatible behavior may be re-introduced in a future release. Until then, the use of ssyyssooppeenn(()), ssyyssrreeaadd(()) and ssyysswwrriittee(()) is not supported for “text” mode operations.

FFuuttuurree DDiirreeccttiioonnss The following things mmiigghhtt happen in future. The first publicly available releases having these characteristics will be the developer releases Perl 5.9.x, culminating in the Perl 5.10.0 release. These are our best guesses at the moment: we reserve the right to rethink.

 •   PerlIO will become The Default.  Currently (in Perl 5.8.x) the stdio
     library is still used if Perl thinks it can use certain tricks to
     make stdio go rreeaallllyy fast.  For future releases our goal is to make
     PerlIO go even faster.

 •   A new feature called _a_s_s_e_r_t_i_o_n_s will be available.  This means that
     one can have code called assertions sprinkled in the code: usually
     they are optimised away, but they can be enabled with the "-A"
     option.

 •   A new operator "//" (defined-or) will be available.  This means that
     one will be able to say

         $a // $b

     instead of

        defined $a ? $a : $b

     and

        $c //= $d;

     instead of

        $c = $d unless defined $c;

     The operator will have the same precedence and associativity as "||".
     A source code patch against the Perl 5.8.1 sources will be available
     in CPAN as _a_u_t_h_o_r_s_/_i_d_/_H_/_H_M_/_H_M_B_R_A_N_D_/_d_o_r_-_5_._8_._1_._d_i_f_f.

 •   "unpack()" will default to unpacking the $_.

 •   Various Copy-On-Write techniques will be investigated in hopes of
     speeding up Perl.

 •   CPANPLUS, Inline, and Module::Build will become core modules.

 •   The ability to write true lexically scoped pragmas will be
     introduced.

 •   Work will continue on the bytecompiler and byteloader.

 •   v-strings as they currently exist are scheduled to be deprecated.
     The v-less form (1.2.3) will become a "version object" when used with
     "use", "require", and $VERSION.  $^V will also be a "version object"
     so the printf("%vd",...) construct will no longer be needed.  The
     v-ful version (v1.2.3) will become obsolete.  The equivalence of
     strings and v-strings (e.g.  that currently 5.8.0 is equal to
     "\5\8\0") will go away.  TThheerree mmaayy bbee nnoo ddeepprreeccaattiioonn wwaarrnniinngg ffoorr
     vv--ssttrriinnggss, though: it is quite hard to detect when v-strings are
     being used safely, and when they are not.

 •   5.005 Threads Will Be Removed

 •   The $* Variable Will Be Removed (it was deprecated a long time ago)

 •   Pseudohashes Will Be Removed

RReeppoorrttiinngg BBuuggss If you find what you think is a bug, you might check the articles recently posted to the comp.lang.perl.misc newsgroup and the perl bug database at http://bugs.perl.org/ . 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 ppeerrllbbuugg 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/

SSEEEE AALLSSOO #

 The _C_h_a_n_g_e_s file for exhaustive details on what changed.

 The _I_N_S_T_A_L_L file for how to build Perl.

 The _R_E_A_D_M_E file for general stuff.

 The _A_r_t_i_s_t_i_c and _C_o_p_y_i_n_g files for copyright information.

perl v5.36.3 2019-02-13 PERL581DELTA(1)