=head1 NAME perldelta - what's new for perl v5.6 (as of v5.005_61) =head1 DESCRIPTION This is an unsupported alpha release, meant for intrepid Perl developers only. The included sources may not even build correctly on some platforms. Subscribing to perl5-porters is the best way to monitor and contribute to the progress of development releases (see www.perl.org for info). This document describes differences between the 5.005 release and this one. =head1 Incompatible Changes =head2 Perl Source Incompatibilities TODO =head2 C Source Incompatibilities =over 4 =item C Release 5.005 grandfathered old global symbol names by providing preprocessor macros for extension source compatibility. As of release 5.6, these preprocessor definitions are not available by default. You need to explicitly compile perl with C<-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 =item C This new build option provides a set of macros for all API functions such that an implicit interpreter/thread context argument is passed to every API function. As a result of this, something like C amounts to a macro invocation that actually translates to something like C. 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 B 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). PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built with one of -Dusethreads, -Dusemultiplicity, or both. See L for detailed information on the ramifications of building Perl using this option. =item C Enabling Perl's malloc in release 5.005 and earlier caused the namespace of system versions of the malloc family of functions to be usurped by the Perl versions, since by default they used the same names. Besides causing problems on platforms that do not allow these functions to be cleanly replaced, this also meant that the system versions could not be called in programs that used Perl's malloc. Previous versions of Perl have allowed this behaviour to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor definitions. As of release 5.6, Perl's malloc family of functions have default names distinct from the system versions. You need to explicitly compile perl with C<-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 B constitute Perl's memory allocation API. See L for further information about that. =item C and C Issues The C global is now thread local, so a C declaration is needed in the scope in which the global appears. XSUBs should handle this automatically, but if you have used C in support functions, you either need to change the C to a local variable (which is recommended), or put in a C. =back =head2 Compatible C Source API Changes =over =item C is now C The cpp macros C, C, and C are now available by default from perl.h, and reflect the base revision, patchlevel, and subversion respectively. C had no prior equivalent, while C and C were previously available as C and C. The new names cause less pollution of the B namespace and reflect what the numbers have come to stand for in common practice. For compatibility, the old names are still supported when F is explicitly included (as required before), so there is no source incompatibility from the change. =back =head2 Binary Incompatibilities The default build of this release is binary compatible with the 5.005 release or its maintenance versions. The usethreads or usemultiplicity builds are B binary compatible with the corresponding builds in 5.005. =head1 Core Changes =head2 Unicode and UTF-8 support Perl can optionally use UTF-8 as its internal representation for character strings. The C pragma enables this support in the current lexical scope. See L for more information. =head2 Lexically scoped warning categories You can now control the granularity of warnings emitted by perl at a finer level using the C pragma. See L and L for details. =head2 Binary numbers supported Binary numbers are now supported as literals, in s?printf formats, and C: $answer = 0b101010; printf "The answer is: %b\n", oct("0b101010"); =head2 syswrite() ease-of-use The length argument of C is now optional. =head2 64-bit support All platforms that have 64-bit integers either (a) natively as longs or ints (b) via special compiler flags (c) using long long are able to use "quads" (64-integers) as follows: =over 4 =item constants in the code =item arguments to oct() and hex() =item arguments to print(), printf() and sprintf() =item pack() and unpack() "q" format =item in basic arithmetics =item vec() (but see the below note about bit arithmetics) =back Note that unless you have the case (a) you will have to configure and compile Perl using the -Duse64bits Configure flag. Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) are not 64-bit clean. 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 (their lower digits). =head2 Large file support 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 that in addition to requiring a proper file system to do this you may also need to adjust your per-process (or even your per-system) maximum filesize limits before running Perl scripts that try to handle large files, especially if you intend to write such files. Adjusting your file system/system limits is outside the scope of Perl. For process limits, you may try to increase the limits using your shell's limit/ulimit command before running Perl. The BSD::Resource extension (not included with the standard Perl distribution) may also be of use. (Large file support is also related to 64-bit support, for obvious reasons) =head2 Better syntax checks on parenthesized unary operators 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 L. =head2 POSIX character class syntax [: :] supported For example to match alphabetic characters use /[[:alpha:]]/. See L for details. =head2 Improved C operator The C operator is now evaluated at compile time into a true list instead of being replaced with a run time call to C. This removes the confusing misbehaviour of C 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". =head2 pack() format 'Z' supported The new format type 'Z' is useful for packing and unpacking null-terminated strings. See L. =head2 pack() format modifier '!' supported The new format type modifier '!' is useful for packing and unpacking native shorts, ints, and longs. See L. =head2 pack() and unpack() support counted strings The template character '#' can be used to specify a counted string type to be packed or unpacked. See L. =head2 $^X variables may now have names longer than one character Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax error. Now variable names that begin with a control character may be arbitrarily long. However, for compatibility reasons, these variables I be written with explicit braces, as C<${^XY}> for example. C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more than one control character, such as C<${^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 C<"$^XYZ"> continues to be synonymous with C<$^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 C<^_>, which may be used by user programs and are guaranteed not to acquire special meaning in any future version of Perl. =head2 C implicit in subroutine attributes 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 C pragma in the body of the subroutine. That can now be accomplished with a declaration syntax, like this: sub mymethod : locked, method ; ... sub mymethod : locked, method { ... } F and F have been updated to keep the attributes with the stubs they provide. See L. =head1 Significant bug fixes =head2 EHANDLEE on empty files With C<$/> set to C, slurping an empty file returns a string of zero length (instead of C, as it used to) the first time the HANDLE is read. Further reads yield C. 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). =head2 C improvements Line numbers (as reflected by caller() and most diagnostics) within C were often incorrect when here documents were involved. This has been corrected. Lexical lookups for variables appearing in C within functions that were themselves called within an C were searching the wrong place for lexicals. The lexical search now correctly ends at the subroutine's block boundary. Parsing of here documents used to be flawed when they appeared as the replacement expression in C. This has been fixed. =head2 Automatic flushing of output buffers 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. =head2 Better diagnostics on meaningless filehandle operations Constructs such as CFHE)> and CFHE)> 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). =head2 Buffered data discarded from input filehandle when dup'ed. C&OLD")> now discards any data that was previously read and buffered in C. The next read operation on C will return the same data as the corresponding operation on C. Formerly, it would have returned the data from the start of the following disk block instead. =head1 Supported Platforms =over 4 =item * VM/ESA is now supported. =item * Siemens BS2000 is now supported under the POSIX Shell. =item * The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread extension. =item * GNU/Hurd is now supported. =item * Rhapsody is now supported. =item * EPOC is is now supported (on Psion 5). =back =head1 New tests =over 4 =item lib/attrs Compatibility tests for C vs the older C. =item lib/io_const IO constants (SEEK_*, _IO*). =item lib/io_dir Directory-related IO methods (new, read, close, rewind, tied delete). =item lib/io_multihomed INET sockets with multi-homed hosts. =item lib/io_poll IO poll(). =item lib/io_unix UNIX sockets. =item op/attrs Regression tests for C and . =item op/filetest File test operators. =item op/lex_assign Verify operations that access pad objects (lexicals and temporaries). =back =head1 Modules and Pragmata =head2 Modules =over 4 =item attributes While used internally by Perl as a pragma, this module also provides a way to fetch subroutine and variable attributes. See L. =item ByteLoader The ByteLoader is a dedication extension to generate and run Perl bytecode. See L. =item B The Perl Compiler suite has been extensively reworked for this release. =item Devel::DProf Devel::DProf, a Perl source code profiler has been added. =item Dumpvalue Added Dumpvalue module provides screen dumps of Perl data. =item Benchmark You can now run tests for I 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)". =item Devel::Peek The Devel::Peek module provides access to the internal representation of Perl variables and data. It is a data debugging tool for the XS programmer. =item Fcntl More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for large (more than 4G) file access (64-bit support is not yet working, though, so no need to get overly excited), Free/Net/OpenBSD locking behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the mask of O_RDONLY, O_WRONLY, and O_RDWR. =item File::Spec New methods have been added to the File::Spec module: 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. =item File::Spec::Functions The new File::Spec::Functions modules provides a function interface to the File::Spec module. Allows shorthand $fullname = catfile($dir1, $dir2, $file); instead of $fullname = File::Spec->catfile($dir1, $dir2, $file); =item Math::BigInt The logical operations CE>, CE>, C<&>, C<|>, and C<~> are now supported on bigints. =item Math::Complex The accessor methods Re, Im, arg, abs, rho, and theta can now also act as mutators (accessor $z->Re(), mutator $z->Re(3)). =item Math::Trig A little bit of radial trigonometry (cylindrical and spherical), radial coordinate conversions, and the great circle distance were added. =item SDBM_File An EXISTS method has been added to this module (and 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. =item Time::Local The timelocal() and timegm() functions used to silently return bogus results when the date exceeded the machine's integer range. They now consistently croak() if the date falls in an unsupported range. =item Win32 The error return value in list context has been changed for all functions that return a list of values. Previously these functions returned a list with a single element C 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 C 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. =item DBM Filters A new feature called "DBM Filters" has been added to all the DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File. DBM Filters add four new methods to each DBM module: 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 L for further information. =back =head2 Pragmata C is now obsolescent, and is only provided for backward-compatibility. It's been replaced by the C syntax. See L and L. C to enable UTF-8 and Unicode support. C allows modules to inherit pragmatic attributes from the caller's context. C is currently the only supported attribute. Lexical warnings pragma, C, to control optional warnings. C to control the behaviour of filetests (C<-r> C<-w> ...). Currently only one subpragma implemented, "use filetest 'access';", that enables the use of 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. =head1 Utility Changes Todo. =head1 Documentation Changes =over 4 =item perlopentut.pod A tutorial on using open() effectively. =item perlreftut.pod A tutorial that introduces the essentials of references. =item perltootc.pod A tutorial on managing class data for object modules. =back =head1 New Diagnostics =item "my sub" not yet implemented (F) Lexically scoped subroutines are not yet implemented. Don't try that yet. =item %s package attribute may clash with future reserved word: %s (W) A lowercase attribute name was used that had a package-specific handler. That name might have a meaning to Perl itself some day, even though it doesn't yet. Perhaps you should use a mixed-case attribute name, instead. See L. =item /%s/: Unrecognized escape \\%c passed through (W) You used a backslash-character combination which is not recognized by Perl. This combination appears in an interpolated variable or a C<'>-delimited regular expression. =item Filehandle %s opened only for output (W) You tried to read from a filehandle opened only for writing. If you intended it to be a read-write filehandle, you needed to open it with "+E" or "+E" or "+EE" instead of with "E" or nothing. If you intended only to read from the file, use "E". See L. =item Invalid %s attribute: %s The indicated attribute for a subroutine or variable was not recognized by Perl or by a user-supplied handler. See L. =item Invalid %s attributes: %s The indicated attributes for a subroutine or variable were not recognized by Perl or by a user-supplied handler. See L. =item Invalid separator character %s in attribute list (F) Something other than a comma or whitespace was seen between the elements of an attribute list. If the previous attribute had a parenthesised parameter list, perhaps that list was terminated too soon. See L. =item Missing command in piped open (W) You used the C or C construction, but the command was missing or blank. =item Missing name in "my sub" (F) The reserved syntax for lexically scoped subroutines requires that they have a name with which they can be found. =item Unrecognized escape \\%c passed through (W) You used a backslash-character combination which is not recognized by Perl. =item Unterminated attribute parameter in attribute list (F) The lexer saw an opening (left) parenthesis character while parsing an attribute list, but the matching closing (right) parenthesis character was not found. You may need to add (or remove) a backslash character to get your parentheses to balance. See L. =item Unterminated attribute list (F) The lexer found something other than a simple identifier at the start of an attribute, and it wasn't a semicolon or the start of a block. Perhaps you terminated the parameter list of the previous attribute too soon. See L. =item defined(@array) is deprecated (D) defined() is not usually useful on arrays because it checks for an undefined I value. If you want to see if the array is empty, just use C for example. =item defined(%hash) is deprecated (D) defined() is not usually useful on hashes because it checks for an undefined I value. If you want to see if the hash is empty, just use C for example. =item Invalid separator character %s in subroutine attribute list (F) Something other than a comma or whitespace was seen between the elements of a subroutine attribute list. If the previous attribute had a parenthesised parameter list, perhaps that list was terminated too soon. =item Unterminated attribute parameter in subroutine attribute list (F) The lexer saw an opening (left) parenthesis character while parsing a subroutine attribute list, but the matching closing (right) parenthesis character was not found. You may need to add (or remove) a backslash character to get your parentheses to balance. =item Unterminated subroutine attribute list (F) The lexer found something other than a simple identifier at the start of a subroutine attribute, and it wasn't a semicolon or the start of a block. Perhaps you terminated the parameter list of the previous attribute too soon. =item /%s/ should probably be written as "%s" (W) You have used a pattern where Perl expected to find a string, like in the first argument to C. 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. =head1 Obsolete Diagnostics Todo. =head1 Configuration Changes =head2 installusrbinperl 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. =head2 SOCKS support You can use "Configure -Dusesocks" which causes Perl to probe for the SOCKS proxy protocol library, http://www.socks.nec.com/ =head1 BUGS If you find what you think is a bug, you might check the headers of 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 B program included with your release. Make sure to trim your bug down to a tiny but sufficient test case. Your bug report, along with the output of C, will be sent off to perlbug@perl.com to be analysed by the Perl porting team. =head1 SEE ALSO The F file for exhaustive details on what changed. The F file for how to build Perl. The F file for general stuff. The F and F files for copyright information. =head1 HISTORY Written by Gurusamy Sarathy >, with many contributions from The Perl Porters. Send omissions or corrections to >. =cut