perl570delta.1

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.\" ========================================================================
.\"
.IX Title "PERL570DELTA 1"
.TH PERL570DELTA 1 "2007-12-18" "perl v5.10.0" "Perl Programmers Reference Guide"
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.SH "NAME"
perl570delta \- what's new for perl v5.7.0
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This document describes differences between the 5.6.0 release and
the 5.7.0 release.
.SH "Security Vulnerability Closed"
.IX Header "Security Vulnerability Closed"
A potential security vulnerability in the optional suidperl 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.  \s-1CERT\s0 and
various vendors have been alerted about the vulnerability.
.PP
The problem was caused by Perl trying to report a suspected 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 compromise 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.
.PP
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 security 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/ ).
.SH "Incompatible Changes"
.IX Header "Incompatible Changes"
.IP "\(bu" 4
Arrays now always interpolate into double-quoted strings:
constructs like \*(L"foo@bar\*(R" now always assume \f(CW@bar\fR is an array,
whether or not the compiler has seen use of \f(CW@bar\fR.
.IP "\(bu" 4
The semantics of bless(\s-1REF\s0, \s-1REF\s0) were unclear and until someone proves
it to make some sense, it is forbidden.
.IP "\(bu" 4
A reference to a reference now stringify as \*(L"\s-1REF\s0(0x81485ec)\*(R" instead
of \*(L"\s-1SCALAR\s0(0x81485ec)\*(R" in order to be more consistent with the return
value of \fIref()\fR.
.IP "\(bu" 4
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.
.IP "\(bu" 4
The obsolete chat2 library that should never have been allowed
to escape the laboratory has been decommissioned.
.IP "\(bu" 4
The unimplemented \s-1POSIX\s0 regex features [[.cc.]] and [[=c=]] are still
recognised but now cause fatal errors.  The previous behaviour of
ignoring them by default and warning if requested was unacceptable
since it, in a way, falsely promised that the features could be used.
.IP "\(bu" 4
The (bogus) escape sequences \e8 and \e9 now give an optional warning
(\*(L"Unrecognized escape passed through\*(R").  There is no need to \e\-escape
any \f(CW\*(C`\ew\*(C'\fR character.
.IP "\(bu" 4
lstat(\s-1FILEHANDLE\s0) now gives a warning because the operation makes no sense.
In future releases this may become a fatal error.
.IP "\(bu" 4
The long deprecated uppercase aliases for the string comparison
operators (\s-1EQ\s0, \s-1NE\s0, \s-1LT\s0, \s-1LE\s0, \s-1GE\s0, \s-1GT\s0) have now been removed.
.IP "\(bu" 4
The regular expression captured submatches ($1, \f(CW$2\fR, ...) are now
more consistently unset if the match fails, instead of leaving false
data lying around in them.
.IP "\(bu" 4
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', ...).
.SH "Core Enhancements"
.IX Header "Core Enhancements"
.IP "\(bu" 4
\&\f(CW\*(C`perl \-d:Module=arg,arg,arg\*(C'\fR now works (previously one couldn't pass
in multiple arguments.)
.IP "\(bu" 4
my _\|_PACKAGE_\|_ \f(CW$obj\fR now works.
.IP "\(bu" 4
\&\f(CW\*(C`no Module;\*(C'\fR now works even if there is no \*(L"sub unimport\*(R" in the Module.
.IP "\(bu" 4
The numerical comparison operators return \f(CW\*(C`undef\*(C'\fR if either operand
is a NaN.  Previously the behaviour was unspecified.
.IP "\(bu" 4
\&\f(CW\*(C`pack(\*(AqU0a*\*(Aq, ...)\*(C'\fR can now be used to force a string to \s-1UTF\-8\s0.
.IP "\(bu" 4
prototype(\e&) is now available.
.IP "\(bu" 4
There is now an \s-1UNTIE\s0 method.
.SH "Modules and Pragmata"
.IX Header "Modules and Pragmata"
.Sh "New Modules"
.IX Subsection "New Modules"
.IP "\(bu" 4
File::Temp allows one to create temporary files and directories in an
easy, portable, and secure way.
.IP "\(bu" 4
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.
.Sh "Updated And Improved Modules and Pragmata"
.IX Subsection "Updated And Improved Modules and Pragmata"
.IP "\(bu" 4
The following independently supported modules have been updated to
newer versions from \s-1CPAN:\s0 \s-1CGI\s0, \s-1CPAN\s0, DB_File, File::Spec, Getopt::Long,
the podlators bundle, Pod::LaTeX, Pod::Parser, Term::ANSIColor, Test.
.IP "\(bu" 4
Bug fixes and minor enhancements have been applied to B::Deparse,
Data::Dumper, IO::Poll, IO::Socket::INET, Math::BigFloat,
Math::Complex, Math::Trig, Net::protoent, the re pragma, SelfLoader,
Sys::SysLog, Test::Harness, Text::Wrap, \s-1UNIVERSAL\s0, and the warnings
pragma.
.IP "\(bu" 4
The \fIattributes::reftype()\fR now works on tied arguments.
.IP "\(bu" 4
AutoLoader can now be disabled with \f(CW\*(C`no AutoLoader;\*(C'\fR,
.IP "\(bu" 4
The English module can now be used without the infamous performance
hit by saying
.Sp
.Vb 1
\&        use English \*(Aq\-no_performance_hit\*(Aq;
.Ve
.Sp
(Assuming, of course, that one doesn't need the troublesome variables
\&\f(CW\*(C`$\`\*(C'\fR, \f(CW$&\fR, or \f(CW\*(C`$\*(Aq\*(C'\fR.)  Also, introduced \f(CW@LAST_MATCH_START\fR and
\&\f(CW@LAST_MATCH_END\fR English aliases for \f(CW\*(C`@\-\*(C'\fR and \f(CW\*(C`@+\*(C'\fR.
.IP "\(bu" 4
File::Find now has pre\- and post-processing callbacks.  It also
correctly changes directories when chasing symbolic links.  Callbacks
(naughtily) exiting with \*(L"next;\*(R" instead of \*(L"return;\*(R" now work.
.IP "\(bu" 4
\&\fIFile::Glob::glob()\fR renamed to \fIFile::Glob::bsd_glob()\fR to avoid
prototype mismatch with \fICORE::glob()\fR.
.IP "\(bu" 4
IPC::Open3 now allows the use of numeric file descriptors.
.IP "\(bu" 4
use lib now works identically to \f(CW@INC\fR.  Removing directories
with 'no lib' now works.
.IP "\(bu" 4
\&\f(CW%INC\fR now localised in a Safe compartment so that use/require work.
.IP "\(bu" 4
The Shell module now has an \s-1OO\s0 interface.
.SH "Utility Changes"
.IX Header "Utility Changes"
.IP "\(bu" 4
The Emacs perl mode (emacs/cperl\-mode.el) has been updated to version
4.31.
.IP "\(bu" 4
Perlbug is now much more robust.  It also sends the bug report to
perl.org, not perl.com.
.IP "\(bu" 4
The perlcc utility has been rewritten and its user interface (that is,
command line) is much more like that of the \s-1UNIX\s0 C compiler, cc.
.IP "\(bu" 4
The xsubpp utility for extension writers now understands \s-1POD\s0
documentation embedded in the *.xs files.
.SH "New Documentation"
.IX Header "New Documentation"
.IP "\(bu" 4
perl56delta details the changes between the 5.005 release and the
5.6.0 release.
.IP "\(bu" 4
perldebtut is a Perl debugging tutorial.
.IP "\(bu" 4
perlebcdic contains considerations for running Perl on \s-1EBCDIC\s0 platforms.
Note that unfortunately \s-1EBCDIC\s0 platforms that used to supported back in
Perl 5.005 are still unsupported by Perl 5.7.0; the plan, however, is to
bring them back to the fold.
.IP "\(bu" 4
perlnewmod tells about writing and submitting a new module.
.IP "\(bu" 4
perlposix-bc explains using Perl on the POSIX-BC platform
(an \s-1EBCDIC\s0 mainframe platform).
.IP "\(bu" 4
perlretut is a regular expression tutorial.
.IP "\(bu" 4
perlrequick is a regular expressions quick-start guide.
Yes, much quicker than perlretut.
.IP "\(bu" 4
perlutil explains the command line utilities packaged with the Perl
distribution.
.SH "Performance Enhancements"
.IX Header "Performance Enhancements"
.IP "\(bu" 4
\&\fImap()\fR that changes the size of the list should now work faster.
.IP "\(bu" 4
\&\fIsort()\fR 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 \fIsort()\fR
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 \fIsort()\fR is now stable (meaning that elements with identical
keys will stay ordered as they were before the sort).
.SH "Installation and Configuration Improvements"
.IX Header "Installation and Configuration Improvements"
.Sh "Generic Improvements"
.IX Subsection "Generic Improvements"
.IP "\(bu" 4
\&\s-1INSTALL\s0 now explains how you can configure Perl to use 64\-bit
integers even on non\-64\-bit platforms.
.IP "\(bu" 4
Policy.sh policy change: if you are reusing a Policy.sh file
(see \s-1INSTALL\s0) and you use Configure \-Dprefix=/foo/bar and in the old
Policy \f(CW$prefix\fR eq \f(CW$siteprefix\fR and \f(CW$prefix\fR eq \f(CW$vendorprefix\fR, all of
them will now be changed to the new prefix, /foo/bar.  (Previously
only \f(CW$prefix\fR changed.)  If you do not like this new behaviour,
specify prefix, siteprefix, and vendorprefix explicitly.
.IP "\(bu" 4
A new optional location for Perl libraries, otherlibdirs, is available.
It can be used for example for vendor add-ons without disturbing Perl's
own library directories.
.IP "\(bu" 4
In many platforms the vendor-supplied 'cc' is too stripped-down to
build Perl (basically, 'cc' doesn't do \s-1ANSI\s0 C).  If this seems
to be the case and 'cc' does not seem to be the \s-1GNU\s0 C compiler
\&'gcc', an automatic attempt is made to find and use 'gcc' instead.
.IP "\(bu" 4
gcc needs to closely track the operating system release to avoid
build problems. If Configure finds that gcc was built for a different