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       This document describes differences between the 5.6.0
       release and the 5.7.0 release.

Security Vulnerability Closed

       A potential security vulnerability in the optional suid­
       perl component of Perl has been identified.  suidperl is
       neither built nor installed by default.  As of September
       the 2nd, 2000, the only known vulnerable platform is
       Linux, most likely all Linux distributions.  CERT and var­
       ious vendors have been alerted about the vulnerability.

       The problem was caused by Perl trying to report a sus­
       pected security exploit attempt using an external program,
       /bin/mail.  On Linux platforms the /bin/mail program had
       an undocumented feature which when combined with suidperl
       gave access to a root shell, resulting in a serious com­
       promise instead of reporting the exploit attempt.  If you
       don't have /bin/mail, or if you have 'safe setuid
       scripts', or if suidperl is not installed, you are safe.

       The exploit attempt reporting feature has been completely
       removed from the Perl 5.7.0 release, so that particular
       vulnerability isn't there anymore.  However, further secu­
       rity vulnerabilities are, unfortunately, always possible.
       The suidperl code is being reviewed and if deemed too
       risky to continue to be supported, it may be completely
       removed from future releases.  In any case, suidperl
       should only be used by security experts who know exactly
       what they are doing and why they are using suidperl
       instead of some other solution such as sudo ( see
       http://www.courtesan.com/sudo/ ).

Incompatible Changes

       ·   Arrays now always interpolate into double-quoted
           strings: constructs like "foo@bar" now always assume
           @bar is an array, whether or not the compiler has seen
           use of @bar.

       ·   The semantics of bless(REF, REF) were unclear and
           until someone proves it to make some sense, it is for­

       ·   A reference to a reference now stringify as
           "REF(0x81485ec)" instead of "SCALAR(0x81485ec)" in
           order to be more consistent with the return value of

       ·   The very dusty examples in the eg/ directory have been
           removed.  Suggestions for new shiny examples welcome
           but the main issue is that the examples need to be
           documented, tested and (most importantly) maintained.
           through").  There is no need to \-escape any "\w"

       ·   lstat(FILEHANDLE) now gives a warning because the
           operation makes no sense.  In future releases this may
           become a fatal error.

       ·   The long deprecated uppercase aliases for the string
           comparison operators (EQ, NE, LT, LE, GE, GT) have now
           been removed.

       ·   The regular expression captured submatches ($1, $2,
           ...) are now more consistently unset if the match
           fails, instead of leaving false data lying around in

       ·   The tr///C and tr///U features have been removed and
           will not return; the interface was a mistake.  Sorry
           about that.  For similar functionality, see pack('U0',
           ...) and pack('C0', ...).

Core Enhancements

       ·   "perl -d:Module=arg,arg,arg" now works (previously one
           couldn't pass in multiple arguments.)

       ·   my __PACKAGE__ $obj now works.

       ·   "no Module;" now works even if there is no "sub unim­
           port" in the Module.

       ·   The numerical comparison operators return "undef" if
           either operand is a NaN.  Previously the behaviour was

       ·   "pack('U0a*', ...)" can now be used to force a string
           to UTF-8.

       ·   prototype(\&) is now available.

       ·   There is now an UNTIE method.

Modules and Pragmata

       New Modules

       ·   File::Temp allows one to create temporary files and
           directories in an easy, portable, and secure way.

       ·   Storable gives persistence to Perl data structures by
           allowing the storage and retrieval of Perl data to and
           from files in a fast and compact binary format.

       ·   The attributes::reftype() now works on tied arguments.

       ·   AutoLoader can now be disabled with "no AutoLoader;",

       ·   The English module can now be used without the infa­
           mous performance hit by saying

                   use English '-no_performance_hit';

           (Assuming, of course, that one doesn't need the trou­
           blesome variables $`, $&, or $'.)  Also, introduced
           @LAST_MATCH_START and @LAST_MATCH_END English aliases
           for "@-" and "@+".

       ·   File::Find now has pre- and post-processing callbacks.
           It also correctly changes directories when chasing
           symbolic links.  Callbacks (naughtily) exiting with
           "next;" instead of "return;" now work.

       ·   File::Glob::glob() renamed to File::Glob::bsd_glob()
           to avoid prototype mismatch with CORE::glob().

       ·   IPC::Open3 now allows the use of numeric file descrip­

       ·   use lib now works identically to @INC.  Removing
           directories with 'no lib' now works.

       ·   %INC now localised in a Safe compartment so that
           use/require work.

       ·   The Shell module now has an OO interface.

Utility Changes

       ·   The Emacs perl mode (emacs/cperl-mode.el) has been
           updated to version 4.31.

       ·   Perlbug is now much more robust.  It also sends the
           bug report to perl.org, not perl.com.

       ·   The perlcc utility has been rewritten and its user
           interface (that is, command line) is much more like
           that of the UNIX C compiler, cc.

       ·   The xsubpp utility for extension writers now under­
           stands POD documentation embedded in the *.xs files.

New Documentation

       ·   perl56delta details the changes between the 5.005
           release and the 5.6.0 release.

       ·   perlretut is a regular expression tutorial.

       ·   perlrequick is a regular expressions quick-start
           guide.  Yes, much quicker than perlretut.

       ·   perlutil explains the command line utilities packaged
           with the Perl distribution.

Performance Enhancements

       ·   map() that changes the size of the list should now
           work faster.

       ·   sort() has been changed to use mergesort internally as
           opposed to the earlier quicksort.  For very small
           lists this may result in slightly slower sorting
           times, but in general the speedup should be at least
           20%.  Additional bonuses are that the worst case
           behaviour of sort() is now better (in computer science
           terms it now runs in time O(N log N), as opposed to
           quicksort's Theta(N**2) worst-case run time
           behaviour), and that sort() is now stable (meaning
           that elements with identical keys will stay ordered as
           they were before the sort).

Installation and Configuration Improvements

       Generic Improvements

       ·   INSTALL now explains how you can configure Perl to use
           64-bit integers even on non-64-bit platforms.

       ·   Policy.sh policy change: if you are reusing a Pol­
           icy.sh file (see INSTALL) and you use Configure -Dpre­
           fix=/foo/bar and in the old Policy $prefix eq
           $siteprefix and $prefix eq $vendorprefix, all of them
           will now be changed to the new prefix, /foo/bar.
           (Previously only $prefix changed.)  If you do not like
           this new behaviour, specify prefix, siteprefix, and
           vendorprefix explicitly.

       ·   A new optional location for Perl libraries, otherlib­
           dirs, is available.  It can be used for example for
           vendor add-ons without disturbing Perl's own library

       ·   In many platforms the vendor-supplied 'cc' is too
           stripped-down to build Perl (basically, 'cc' doesn't
           do ANSI C).  If this seems to be the case and 'cc'
           does not seem to be the GNU C compiler 'gcc', an auto­
           matic attempt is made to find and use 'gcc' instead.

       ·   gcc needs to closely track the operating system
       ·   installperl now outputs everything to STDERR.

       ·   $Config{byteorder} is now computed dynamically (this
           is more robust with "fat binaries" where an executable
           image contains binaries for more than one binary plat­

Selected Bug Fixes

       ·   Several debugger fixes: exit code now reflects the
           script exit code, condition "0" now treated correctly,
           the "d" command now checks line number, the $. no
           longer gets corrupted, all debugger output now goes
           correctly to the socket if RemotePort is set.

       ·   *foo{FORMAT} now works.

       ·   Lexical warnings now propagating correctly between

       ·   Line renumbering with eval and "#line" now works.

       ·   Fixed numerous memory leaks, especially in eval "".

       ·   Modulus of unsigned numbers now works (4063328477 %
           65535 used to return 27406, instead of 27047).

       ·   Some "not a number" warnings introduced in 5.6.0 elim­
           inated to be more compatible with 5.005.  Infinity is
           now recognised as a number.

       ·   our() variables will not cause "will not stay shared"

       ·   pack "Z" now correctly terminates the string with

       ·   Fix password routines which in some shadow password
           platforms (e.g. HP-UX) caused getpwent() to return
           every other entry.

       ·   printf() no longer resets the numeric locale to "C".

       ·   "q(a\\b)" now parses correctly as 'a\\b'.

       ·   Printing quads (64-bit integers) with printf/sprintf
           now works without the q L ll prefixes (assuming you
           are on a quad-capable platform).

       ·   Regular expressions on references and overloaded
           scalars now work.

       ·   scalar() now forces scalar context even when used in

       ·   Allow read-only string on left hand side of non-modi­
           fying tr///.

       ·   Several Unicode fixes (but still not perfect).

           ·       BOMs (byte order marks) in the beginning of
                   Perl files (scripts, modules) should now be
                   transparently skipped.  UTF-16 (UCS-2) encoded
                   Perl files should now be read correctly.

           ·       The character tables have been updated to Uni­
                   code 3.0.1.

           ·       chr() for values greater than 127 now create
                   utf8 when under use utf8.

           ·       Comparing with utf8 data does not magically
                   upgrade non-utf8 data into utf8.

           ·       "IsAlnum", "IsAlpha", and "IsWord" now match

           ·       Concatenation with the "." operator or via
                   variable interpolation, "eq", "substr",
                   "reverse", "quotemeta", the "x" operator, sub­
                   stitution with "s///", single-quoted UTF-8,
                   should now work--in theory.

           ·       The "tr///" operator now works slightly better
                   but is still rather broken.  Note that the
                   "tr///CU" functionality has been removed (but
                   see pack('U0', ...)).

           ·       vec() now refuses to deal with characters

           ·       Zero entries were missing from the Unicode
                   classes like "IsDigit".

       ·   UNIVERSAL::isa no longer caches methods incorrectly.
           (This broke the Tk extension with 5.6.0.)

       Platform Specific Changes and Fixes

       ·   BSDI 4.*

           Perl now works on post-4.0 BSD/OSes.

       ·   All BSDs

           Perl now works on post-3.0 FreeBSDs.

       ·   HP-UX

           README.hpux updated; "Configure -Duse64bitall" now
           almost works.

       ·   IRIX

           Numerous compilation flag and hint enhancements; acci­
           dental mixing of 32-bit and 64-bit libraries (a doomed
           attempt) made much harder.

       ·   Linux

           Long doubles should now work (see INSTALL).

       ·   Mac OS Classic

           Compilation of the standard Perl distribution in Mac
           OS Classic should now work if you have the Metrowerks
           development environment and the missing Mac-specific
           toolkit bits.  Contact the macperl mailing list for

       ·   MPE/iX

           MPE/iX update after Perl 5.6.0.  See README.mpeix.

       ·   NetBSD/sparc

           Perl now works on NetBSD/sparc.

       ·   OS/2

           Now works with usethreads (see INSTALL).

       ·   Solaris

           64-bitness using the Sun Workshop compiler now works.

       ·   Tru64 (aka Digital UNIX, aka DEC OSF/1)

           The operating system version letter now recorded in
           $Config{osvers}.  Allow compiling with gcc (previously
           explicitly forbidden).  Compiling with gcc still not
           recommended because buggy code results, even with gcc

       ·   Unicos

           ·       accept() no longer leaks memory.

           ·       Better chdir() return value for a non-existent

           ·       New %ENV entries now propagate to subpro­

           ·       $ENV{LIB} now used to search for libs under
                   Visual C.

           ·       A failed (pseudo)fork now returns undef and
                   sets errno to EAGAIN.

           ·       Allow REG_EXPAND_SZ keys in the registry.

           ·       Can now send() from all threads, not just the
                   first one.

           ·       Fake signal handling reenabled, bugs and all.

           ·       Less stack reserved per thread so that more
                   threads can run concurrently. (Still 16M per

           ·       "File::Spec->tmpdir()" now prefers C:/temp
                   over /tmp (works better when perl is running
                   as service).

           ·       Better UNC path handling under ithreads.

           ·       wait() and waitpid() now work much better.

           ·       winsock handle leak fixed.

New or Changed Diagnostics

       All regular expression compilation error messages are now
       hopefully easier to understand both because the error mes­
       sage now comes before the failed regex and because the
       point of failure is now clearly marked.

       The various "opened only for", "on closed", "never opened"
       warnings drop the "main::" prefix for filehandles in the
       "main" package, for example "STDIN" instead of

       The "Unrecognized escape" warning has been extended to
       include "\8", "\9", and "\_".  There is no need to escape
       any of the "\w" characters.

Changed Internals

       ·   perlapi.pod (a companion to perlguts) now attempts to

       ·   Added is_utf8_char(), is_utf8_string(),
           bytes_to_utf8(), and utf8_to_bytes().

       ·   Now xsubs can have attributes just like subs.

Known Problems

       Unicode Support Still Far From Perfect

       We're working on it.  Stay tuned.

       EBCDIC Still A Lost Platform

       The plan is to bring them back.

       Building Extensions Can Fail Because Of Largefiles

       Certain extensions like mod_perl and BSD::Resource are
       known to have issues with `largefiles', a change brought
       by Perl 5.6.0 in which file offsets default to 64 bits
       wide, where supported.  Modules may fail to compile at all
       or compile and work incorrectly.  Currently there is no
       good solution for the problem, but Configure now provides
       appropriate non-largefile ccflags, ldflags, libswanted,
       and libs in the %Config hash (e.g., $Con­
       fig{ccflags_nolargefiles}) so the extensions that are hav­
       ing problems can try configuring themselves without the
       largefileness.  This is admittedly not a clean solution,
       and the solution may not even work at all.  One potential
       failure is whether one can (or, if one can, whether it's a
       good idea) link together at all binaries with different
       ideas about file offsets, all this is platform-dependent.

       ftmp-security tests warn 'system possibly insecure'

       Don't panic.  Read INSTALL 'make test' section instead.

       Test lib/posix Subtest 9 Fails In LP64-Configured HP-UX

       If perl is configured with -Duse64bitall, the successful
       result of the subtest 10 of lib/posix may arrive before
       the successful result of the subtest 9, which confuses the
       test harness so much that it thinks the subtest 9 failed.

       Long Doubles Still Don't Work In Solaris

       The experimental long double support is still very much so
       in Solaris.  (Other platforms like Linux and Tru64 are
       beginning to solidify in this area.)

       Linux With Sfio Fails op/misc Test 48

       ·   DOS DJGPP may hang when testing Storable.

       ·   st-06compat fails in UNICOS and UNICOS/mk.

           This means that you cannot read old (pre-Storable-0.7)
           Storable images made in other platforms.

       ·   st-store.t and st-retrieve may fail with Compaq C 6.2
           on OpenVMS Alpha 7.2.

       Threads Are Still Experimental

       Multithreading is still an experimental feature.  Some
       platforms emit the following message for lib/thr5005

           # This is a KNOWN FAILURE, and one of the reasons why threading
           # is still an experimental feature.  It is here to stop people
           # from deploying threads in production. ;-)

       and another known thread-related warning is

          pragma/overload......Unbalanced saves: 3 more saves than restores
          panic: magic_mutexfree during global destruction.
          lib/selfloader.......Unbalanced saves: 3 more saves than restores
          panic: magic_mutexfree during global destruction.
          lib/st-dclone........Unbalanced saves: 3 more saves than restores
          panic: magic_mutexfree during global destruction.

       The Compiler Suite Is Still Experimental

       The compiler suite is slowly getting better but is nowhere
       near working order yet.  The backend part that has seen
       perhaps the most progress is the bytecode compiler.

Reporting Bugs

       If you find what you think is a bug, you might check the
       articles recently posted to the comp.lang.perl.misc news­
       group and the perl bug database at http://bugs.perl.org/
       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
       tributions from The Perl Porters and Perl Users submitting
       feedback and patches.

       Send omissions or corrections to <perlbug@perl.org>.

perl v5.8.1                 2003-09-02            PERL570DELTA(1)

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