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perl5004delta



DESCRIPTION

       This document describes differences between the 5.003
       release (as documented in Programming Perl, second edi­
       tion--the Camel Book) and this one.


Supported Environments

       Perl5.004 builds out of the box on Unix, Plan 9, LynxOS,
       VMS, OS/2, QNX, AmigaOS, and Windows NT.  Perl runs on
       Windows 95 as well, but it cannot be built there, for lack
       of a reasonable command interpreter.


Core Changes

       Most importantly, many bugs were fixed, including several
       security problems.  See the Changes file in the distribu­
       tion for details.

       List assignment to %ENV works

       "%ENV = ()" and "%ENV = @list" now work as expected
       (except on VMS where it generates a fatal error).

       Change to "Can't locate Foo.pm in @INC" error

       The error "Can't locate Foo.pm in @INC" now lists the con­
       tents of @INC for easier debugging.

       Compilation option: Binary compatibility with 5.003

       There is a new Configure question that asks if you want to
       maintain binary compatibility with Perl 5.003.  If you
       choose binary compatibility, you do not have to recompile
       your extensions, but you might have symbol conflicts if
       you embed Perl in another application, just as in the
       5.003 release.  By default, binary compatibility is pre­
       served at the expense of symbol table pollution.

       $PERL5OPT environment variable

       You may now put Perl options in the $PERL5OPT environment
       variable.  Unless Perl is running with taint checks, it
       will interpret this variable as if its contents had
       appeared on a "#!perl" line at the beginning of your
       script, except that hyphens are optional.  PERL5OPT may
       only be used to set the following switches: -[DIMUdmw].

       Limitations on -M, -m, and -T options

       The "-M" and "-m" options are no longer allowed on the
       "#!" line of a script.  If a script needs a module, it
       should invoke it with the "use" pragma.

       The -T option is also forbidden on the "#!" line of a
       chance of -T being found on the command line before it is
       found on the "#!" line.

       More precise warnings

       If you removed the -w option from your Perl 5.003 scripts
       because it made Perl too verbose, we recommend that you
       try putting it back when you upgrade to Perl 5.004.  Each
       new perl version tends to remove some undesirable warn­
       ings, while adding new warnings that may catch bugs in
       your scripts.

       Deprecated: Inherited "AUTOLOAD" for non-methods

       Before Perl 5.004, "AUTOLOAD" functions were looked up as
       methods (using the @ISA hierarchy), even when the function
       to be autoloaded was called as a plain function (e.g.
       "Foo::bar()"), not a method (e.g. "Foo->bar()" or
       "$obj->bar()").

       Perl 5.005 will use method lookup only for methods'
       "AUTOLOAD"s.  However, there is a significant base of
       existing code that may be using the old behavior.  So, as
       an interim step, Perl 5.004 issues an optional warning
       when a non-method uses an inherited "AUTOLOAD".

       The simple rule is:  Inheritance will not work when
       autoloading non-methods.  The simple fix for old code is:
       In any module that used to depend on inheriting "AUTOLOAD"
       for non-methods from a base class named "BaseClass", exe­
       cute "*AUTOLOAD = \&BaseClass::AUTOLOAD" during startup.

       Previously deprecated %OVERLOAD is no longer usable

       Using %OVERLOAD to define overloading was deprecated in
       5.003.  Overloading is now defined using the overload
       pragma. %OVERLOAD is still used internally but should not
       be used by Perl scripts. See overload for more details.

       Subroutine arguments created only when they're modified

       In Perl 5.004, nonexistent array and hash elements used as
       subroutine parameters are brought into existence only if
       they are actually assigned to (via @_).

       Earlier versions of Perl vary in their handling of such
       arguments.  Perl versions 5.002 and 5.003 always brought
       them into existence.  Perl versions 5.000 and 5.001
       brought them into existence only if they were not the
       first argument (which was almost certainly a bug).  Ear­
       lier versions of Perl never brought them into existence.


       The $) special variable has always (well, in Perl 5, at
       least) reflected not only the current effective group, but
       also the group list as returned by the "getgroups()" C
       function (if there is one).  However, until this release,
       there has not been a way to call the "setgroups()" C func­
       tion from Perl.

       In Perl 5.004, assigning to $) is exactly symmetrical with
       examining it: The first number in its string value is used
       as the effective gid; if there are any numbers after the
       first one, they are passed to the "setgroups()" C function
       (if there is one).

       Fixed parsing of $$<digit>, &$<digit>, etc.

       Perl versions before 5.004 misinterpreted any type marker
       followed by "$" and a digit.  For example, "$$0" was
       incorrectly taken to mean "${$}0" instead of "${$0}".
       This bug is (mostly) fixed in Perl 5.004.

       However, the developers of Perl 5.004 could not fix this
       bug completely, because at least two widely-used modules
       depend on the old meaning of "$$0" in a string.  So Perl
       5.004 still interprets "$$<digit>" in the old (broken) way
       inside strings; but it generates this message as a warn­
       ing.  And in Perl 5.005, this special treatment will
       cease.

       Fixed localization of $<digit>, $&, etc.

       Perl versions before 5.004 did not always properly local­
       ize the regex-related special variables.  Perl 5.004 does
       localize them, as the documentation has always said it
       should.  This may result in $1, $2, etc. no longer being
       set where existing programs use them.

       No resetting of $. on implicit close

       The documentation for Perl 5.0 has always stated that $.
       is not reset when an already-open file handle is reopened
       with no intervening call to "close".  Due to a bug, perl
       versions 5.000 through 5.003 did reset $. under that cir­
       cumstance; Perl 5.004 does not.

       "wantarray" may return undef

       The "wantarray" operator returns true if a subroutine is
       expected to return a list, and false otherwise.  In Perl
       5.004, "wantarray" can also return the undefined value if
       a subroutine's return value will not be used at all, which
       allows subroutines to avoid a time-consuming calculation
           @a = qw(time now is time);
           print eval @a;
           print '|', scalar eval @a;

       used to print something like "timenowis881399109|4", but
       now (and in perl4) prints "4|4".

       Changes to tainting checks

       A bug in previous versions may have failed to detect some
       insecure conditions when taint checks are turned on.
       (Taint checks are used in setuid or setgid scripts, or
       when explicitly turned on with the "-T" invocation
       option.)  Although it's unlikely, this may cause a previ­
       ously-working script to now fail -- which should be con­
       strued as a blessing, since that indicates a potentially-
       serious security hole was just plugged.

       The new restrictions when tainting include:

       No glob() or <*>
           These operators may spawn the C shell (csh), which
           cannot be made safe.  This restriction will be lifted
           in a future version of Perl when globbing is imple­
           mented without the use of an external program.

       No spawning if tainted $CDPATH, $ENV, $BASH_ENV
           These environment variables may alter the behavior of
           spawned programs (especially shells) in ways that sub­
           vert security.  So now they are treated as dangerous,
           in the manner of $IFS and $PATH.

       No spawning if tainted $TERM doesn't look like a terminal
       name
           Some termcap libraries do unsafe things with $TERM.
           However, it would be unnecessarily harsh to treat all
           $TERM values as unsafe, since only shell metacharac­
           ters can cause trouble in $TERM.  So a tainted $TERM
           is considered to be safe if it contains only alphanu­
           merics, underscores, dashes, and colons, and unsafe if
           it contains other characters (including whitespace).

       New Opcode module and revised Safe module

       A new Opcode module supports the creation, manipulation
       and application of opcode masks.  The revised Safe module
       has a new API and is implemented using the new Opcode mod­
       ule.  Please read the new Opcode and Safe documentation.

       Embedding improvements

       In older versions of Perl it was not possible to create
       and IO::File.  We suggest, but do not require, that you
       use the IO::* modules in new code.

       In harmony with this change, *GLOB{FILEHANDLE} is now just
       a backward-compatible synonym for *GLOB{IO}.

       Internal change: PerlIO abstraction interface

       It is now possible to build Perl with AT&T's sfio IO pack­
       age instead of stdio.  See perlapio for more details, and
       the INSTALL file for how to use it.

       New and changed syntax

       $coderef->(PARAMS)
           A subroutine reference may now be suffixed with an
           arrow and a (possibly empty) parameter list.  This
           syntax denotes a call of the referenced subroutine,
           with the given parameters (if any).

           This new syntax follows the pattern of
           "$hashref->{FOO}" and "$aryref->[$foo]": You may now
           write "&$subref($foo)" as "$subref->($foo)".  All
           these arrow terms may be chained; thus,
           "&{$table->{FOO}}($bar)" may now be written
           "$table->{FOO}->($bar)".

       New and changed builtin constants

       __PACKAGE__
           The current package name at compile time, or the unde­
           fined value if there is no current package (due to a
           "package;" directive).  Like "__FILE__" and
           "__LINE__", "__PACKAGE__" does not interpolate into
           strings.

       New and changed builtin variables

       $^E Extended error message on some platforms.  (Also known
           as $EXTENDED_OS_ERROR if you "use English").

       $^H The current set of syntax checks enabled by "use
           strict".  See the documentation of "strict" for more
           details.  Not actually new, but newly documented.
           Because it is intended for internal use by Perl core
           components, there is no "use English" long name for
           this variable.

       $^M By default, running out of memory it is not trappable.
       New and changed builtin functions

       delete on slices
           This now works.  (e.g. "delete @ENV{'PATH', 'MAN­
           PATH'}")

       flock
           is now supported on more platforms, prefers fcntl to
           lockf when emulating, and always flushes before
           (un)locking.

       printf and sprintf
           Perl now implements these functions itself; it doesn't
           use the C library function sprintf() any more, except
           for floating-point numbers, and even then only known
           flags are allowed.  As a result, it is now possible to
           know which conversions and flags will work, and what
           they will do.

           The new conversions in Perl's sprintf() are:

              %i   a synonym for %d
              %p   a pointer (the address of the Perl value, in hexadecimal)
              %n   special: *stores* the number of characters output so far
                   into the next variable in the parameter list

           The new flags that go between the "%" and the conver­
           sion are:

              #    prefix octal with "0", hex with "0x"
              h    interpret integer as C type "short" or "unsigned short"
              V    interpret integer as Perl's standard integer type

           Also, where a number would appear in the flags, an
           asterisk ("*") may be used instead, in which case Perl
           uses the next item in the parameter list as the given
           number (that is, as the field width or precision).  If
           a field width obtained through "*" is negative, it has
           the same effect as the '-' flag: left-justification.

           See "sprintf" in perlfunc for a complete list of con­
           version and flags.

       keys as an lvalue
           As an lvalue, "keys" allows you to increase the number
           of hash buckets allocated for the given hash.  This
           can gain you a measure of efficiency if you know the
           hash is going to get big.  (This is similar to pre-
           extending an array by assigning a larger number to
           $#array.)  If you say


               while (defined(my $line = <>)) {
                   $line = lc $line;
               } continue {
                   print $line;
               }

               if ((my $answer = <STDIN>) =~ /^y(es)?$/i) {
                   user_agrees();
               } elsif ($answer =~ /^n(o)?$/i) {
                   user_disagrees();
               } else {
                   chomp $answer;
                   die "`$answer' is neither `yes' nor `no'";
               }

           Also, you can declare a foreach loop control variable
           as lexical by preceding it with the word "my".  For
           example, in:

               foreach my $i (1, 2, 3) {
                   some_function();
               }

           $i is a lexical variable, and the scope of $i extends
           to the end of the loop, but not beyond it.

           Note that you still cannot use my() on global punctua­
           tion variables such as $_ and the like.

       pack() and unpack()
           A new format 'w' represents a BER compressed integer
           (as defined in ASN.1).  Its format is a sequence of
           one or more bytes, each of which provides seven bits
           of the total value, with the most significant first.
           Bit eight of each byte is set, except for the last
           byte, in which bit eight is clear.

           If 'p' or 'P' are given undef as values, they now gen­
           erate a NULL pointer.

           Both pack() and unpack() now fail when their templates
           contain invalid types.  (Invalid types used to be
           ignored.)

       sysseek()
           The new sysseek() operator is a variant of seek() that
           sets and gets the file's system read/write position,
           using the lseek(2) system call.  It is the only reli­
           able way to seek before using sysread() or syswrite().
           Its return value is the new position, or the undefined
           value on failure.

       use Module VERSION LIST
           If the VERSION argument is present between Module and
           LIST, then the "use" will call the VERSION method in
           class Module with the given version as an argument.
           The default VERSION method, inherited from the UNIVER­
           SAL class, croaks if the given version is larger than
           the value of the variable $Module::VERSION.  (Note
           that there is not a comma after VERSION!)

           This version-checking mechanism is similar to the one
           currently used in the Exporter module, but it is
           faster and can be used with modules that don't use the
           Exporter.  It is the recommended method for new code.

       prototype(FUNCTION)
           Returns the prototype of a function as a string (or
           "undef" if the function has no prototype).  FUNCTION
           is a reference to or the name of the function whose
           prototype you want to retrieve.  (Not actually new;
           just never documented before.)

       srand
           The default seed for "srand", which used to be "time",
           has been changed.  Now it's a heady mix of difficult-
           to-predict system-dependent values, which should be
           sufficient for most everyday purposes.

           Previous to version 5.004, calling "rand" without
           first calling "srand" would yield the same sequence of
           random numbers on most or all machines.  Now, when
           perl sees that you're calling "rand" and haven't yet
           called "srand", it calls "srand" with the default
           seed. You should still call "srand" manually if your
           code might ever be run on a pre-5.004 system, of
           course, or if you want a seed other than the default.

       $_ as Default
           Functions documented in the Camel to default to $_ now
           in fact do, and all those that do are so documented in
           perlfunc.

       "m//gc" does not reset search position on failure
           The "m//g" match iteration construct has always reset
           its target string's search position (which is visible
           through the "pos" operator) when a match fails; as a
           result, the next "m//g" match after a failure starts
           again at the beginning of the string.  With Perl
           5.004, this reset may be disabled by adding the "c"
           (for "continue") modifier, i.e. "m//gc".  This fea­
           ture, in conjunction with the "\G" zero-width asser­
           tion, makes it possible to chain matches together.

       formats work right on changing lexicals
           Just like anonymous functions that contain lexical
           variables that change (like a lexical index variable
           for a "foreach" loop), formats now work properly.  For
           example, this silently failed before (printed only
           zeros), but is fine now:

               my $i;
               foreach $i ( 1 .. 10 ) {
                   write;
               }
               format =
                   my i is @#
                   $i
               .

           However, it still fails (without a warning) if the
           foreach is within a subroutine:

               my $i;
               sub foo {
                 foreach $i ( 1 .. 10 ) {
                   write;
                 }
               }
               foo;
               format =
                   my i is @#
                   $i
               .

       New builtin methods

       The "UNIVERSAL" package automatically contains the follow­
       ing methods that are inherited by all other classes:

       isa(CLASS)
           "isa" returns true if its object is blessed into a
           subclass of "CLASS"

           "isa" is also exportable and can be called as a sub
           with two arguments. This allows the ability to check
           what a reference points to. Example:

               use UNIVERSAL qw(isa);

               if(isa($ref, 'ARRAY')) {
                  ...
               }

       can(METHOD)
           "can" checks to see if its object has a method called
               # implies:
               A->VERSION(1.2);

       NOTE: "can" directly uses Perl's internal code for method
       lookup, and "isa" uses a very similar method and caching
       strategy. This may cause strange effects if the Perl code
       dynamically changes @ISA in any package.

       You may add other methods to the UNIVERSAL class via Perl
       or XS code.  You do not need to "use UNIVERSAL" in order
       to make these methods available to your program.  This is
       necessary only if you wish to have "isa" available as a
       plain subroutine in the current package.

       TIEHANDLE now supported

       See perltie for other kinds of tie()s.

       TIEHANDLE classname, LIST
           This is the constructor for the class.  That means it
           is expected to return an object of some sort. The ref­
           erence can be used to hold some internal information.

               sub TIEHANDLE {
                   print "<shout>\n";
                   my $i;
                   return bless \$i, shift;
               }

       PRINT this, LIST
           This method will be triggered every time the tied han­
           dle is printed to.  Beyond its self reference it also
           expects the list that was passed to the print func­
           tion.

               sub PRINT {
                   $r = shift;
                   $$r++;
                   return print join( $, => map {uc} @_), $\;
               }

       PRINTF this, LIST
           This method will be triggered every time the tied han­
           dle is printed to with the "printf()" function.
           Beyond its self reference it also expects the format
           and list that was passed to the printf function.

               sub PRINTF {
                   shift;
                     my $fmt = shift;
                   print sprintf($fmt, @_)."\n";
               }

           This method will be called when the handle is read
           from. The method should return undef when there is no
           more data.

               sub READLINE {
                   $r = shift;
                   return "PRINT called $$r times\n"
               }

       GETC this
           This method will be called when the "getc" function is
           called.

               sub GETC { print "Don't GETC, Get Perl"; return "a"; }

       DESTROY this
           As with the other types of ties, this method will be
           called when the tied handle is about to be destroyed.
           This is useful for debugging and possibly for cleaning
           up.

               sub DESTROY {
                   print "</shout>\n";
               }

       Malloc enhancements

       If perl is compiled with the malloc included with the perl
       distribution (that is, if "perl -V:d_mymalloc" is
       'define') then you can print memory statistics at runtime
       by running Perl thusly:

         env PERL_DEBUG_MSTATS=2 perl your_script_here

       The value of 2 means to print statistics after compilation
       and on exit; with a value of 1, the statistics are printed
       only on exit.  (If you want the statistics at an arbitrary
       time, you'll need to install the optional module
       Devel::Peek.)

       Three new compilation flags are recognized by malloc.c.
       (They have no effect if perl is compiled with system mal­
       loc().)

       -DPERL_EMERGENCY_SBRK
           If this macro is defined, running out of memory need
           not be a fatal error: a memory pool can allocated by
           assigning to the special variable $^M.  See "$^M".

       -DPACK_MALLOC
           Perl memory allocation is by bucket with sizes close
           to powers of two.  Because of these malloc overhead
           Similarly to "PACK_MALLOC", this macro improves allo­
           cations of data with size close to a power of two; but
           this works for big allocations (starting with 16K by
           default).  Such allocations are typical for big hashes
           and special-purpose scripts, especially image process­
           ing.

           On recent systems, the fact that perl requires 2M from
           system for 1M allocation will not affect speed of exe­
           cution, since the tail of such a chunk is not going to
           be touched (and thus will not require real memory).
           However, it may result in a premature out-of-memory
           error.  So if you will be manipulating very large
           blocks with sizes close to powers of two, it would be
           wise to define this macro.

           Expected saving of memory is 0-100% (100% in applica­
           tions which require most memory in such 2**n chunks);
           expected slowdown is negligible.

       Miscellaneous efficiency enhancements

       Functions that have an empty prototype and that do nothing
       but return a fixed value are now inlined (e.g. "sub PI ()
       { 3.14159 }").

       Each unique hash key is only allocated once, no matter how
       many hashes have an entry with that key.  So even if you
       have 100 copies of the same hash, the hash keys never have
       to be reallocated.


Support for More Operating Systems

       Support for the following operating systems is new in Perl
       5.004.

       Win32

       Perl 5.004 now includes support for building a "native"
       perl under Windows NT, using the Microsoft Visual C++ com­
       piler (versions 2.0 and above) or the Borland C++ compiler
       (versions 5.02 and above).  The resulting perl can be used
       under Windows 95 (if it is installed in the same directory
       locations as it got installed in Windows NT).  This port
       includes support for perl extension building tools like
       MakeMaker and h2xs, so that many extensions available on
       the Comprehensive Perl Archive Network (CPAN) can now be
       readily built under Windows NT.  See http://www.perl.com/
       for more information on CPAN and README.win32 in the perl
       distribution for more details on how to get started with
       building this port.

       There is also support for building perl under the Cygwin32
       See README.qnx in the perl distribution.

       AmigaOS

       See README.amigaos in the perl distribution.


Pragmata

       Six new pragmatic modules exist:

       use autouse MODULE => qw(sub1 sub2 sub3)
           Defers "require MODULE" until someone calls one of the
           specified subroutines (which must be exported by MOD­
           ULE).  This pragma should be used with caution, and
           only when necessary.

       use blib
       use blib 'dir'
           Looks for MakeMaker-like 'blib' directory structure
           starting in dir (or current directory) and working
           back up to five levels of parent directories.

           Intended for use on command line with -M option as a
           way of testing arbitrary scripts against an unin­
           stalled version of a package.

       use constant NAME => VALUE
           Provides a convenient interface for creating compile-
           time constants, See "Constant Functions" in perlsub.

       use locale
           Tells the compiler to enable (or disable) the use of
           POSIX locales for builtin operations.

           When "use locale" is in effect, the current LC_CTYPE
           locale is used for regular expressions and case map­
           ping; LC_COLLATE for string ordering; and LC_NUMERIC
           for numeric formatting in printf and sprintf (but not
           in print).  LC_NUMERIC is always used in write, since
           lexical scoping of formats is problematic at best.

           Each "use locale" or "no locale" affects statements to
           the end of the enclosing BLOCK or, if not inside a
           BLOCK, to the end of the current file.  Locales can be
           switched and queried with POSIX::setlocale().

           See perllocale for more information.

       use ops
           Disable unsafe opcodes, or any named opcodes, when
           compiling Perl code.

       use vmsish

           Module   Required Version for Perl 5.004
           ------   -------------------------------
           Filter   Filter-1.12
           LWP      libwww-perl-5.08
           Tk       Tk400.202 (-w makes noise)

       Also, the majordomo mailing list program, version 1.94.1,
       doesn't work with Perl 5.004 (nor with perl 4), because it
       executes an invalid regular expression.  This bug is fixed
       in majordomo version 1.94.2.

       Installation directories

       The installperl script now places the Perl source files
       for extensions in the architecture-specific library direc­
       tory, which is where the shared libraries for extensions
       have always been.  This change is intended to allow admin­
       istrators to keep the Perl 5.004 library directory
       unchanged from a previous version, without running the
       risk of binary incompatibility between extensions' Perl
       source and shared libraries.

       Module information summary

       Brand new modules, arranged by topic rather than strictly
       alphabetically:

           CGI.pm               Web server interface ("Common Gateway Interface")
           CGI/Apache.pm        Support for Apache's Perl module
           CGI/Carp.pm          Log server errors with helpful context
           CGI/Fast.pm          Support for FastCGI (persistent server process)
           CGI/Push.pm          Support for server push
           CGI/Switch.pm        Simple interface for multiple server types

           CPAN                 Interface to Comprehensive Perl Archive Network
           CPAN::FirstTime      Utility for creating CPAN configuration file
           CPAN::Nox            Runs CPAN while avoiding compiled extensions

           IO.pm                Top-level interface to IO::* classes
           IO/File.pm           IO::File extension Perl module
           IO/Handle.pm         IO::Handle extension Perl module
           IO/Pipe.pm           IO::Pipe extension Perl module
           IO/Seekable.pm       IO::Seekable extension Perl module
           IO/Select.pm         IO::Select extension Perl module
           IO/Socket.pm         IO::Socket extension Perl module

           Opcode.pm            Disable named opcodes when compiling Perl code

           ExtUtils/Embed.pm    Utilities for embedding Perl in C programs
           ExtUtils/testlib.pm  Fixes up @INC to use just-built extension

           Time/localtime.pm    By-name interface to Perl's builtin localtime
           Time/tm.pm           Internal object for Time::{gm,local}time
           User/grent.pm        By-name interface to Perl's builtin getgr*
           User/pwent.pm        By-name interface to Perl's builtin getpw*

           Tie/RefHash.pm       Base class for tied hashes with references as keys

           UNIVERSAL.pm         Base class for *ALL* classes

       Fcntl

       New constants in the existing Fcntl modules are now sup­
       ported, provided that your operating system happens to
       support them:

           F_GETOWN F_SETOWN
           O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC
           O_EXLOCK O_SHLOCK

       These constants are intended for use with the Perl opera­
       tors sysopen() and fcntl() and the basic database modules
       like SDBM_File.  For the exact meaning of these and other
       Fcntl constants please refer to your operating system's
       documentation for fcntl() and open().

       In addition, the Fcntl module now provides these constants
       for use with the Perl operator flock():

               LOCK_SH LOCK_EX LOCK_NB LOCK_UN

       These constants are defined in all environments (because
       where there is no flock() system call, Perl emulates it).
       However, for historical reasons, these constants are not
       exported unless they are explicitly requested with the
       ":flock" tag (e.g. "use Fcntl ':flock'").

       IO

       The IO module provides a simple mechanism to load all the
       IO modules at one go.  Currently this includes:

            IO::Handle
            IO::Seekable
            IO::File
            IO::Pipe
            IO::Socket

       For more information on any of these modules, please see
       its respective documentation.

       Math::Complex

           csch sech coth
           asinh acosh atanh
           acsch asech acoth
           cplx cplxe

       Math::Trig

       This new module provides a simpler interface to parts of
       Math::Complex for those who need trigonometric functions
       only for real numbers.

       DB_File

       There have been quite a few changes made to DB_File. Here
       are a few of the highlights:

       ·   Fixed a handful of bugs.

       ·   By public demand, added support for the standard hash
           function exists().

       ·   Made it compatible with Berkeley DB 1.86.

       ·   Made negative subscripts work with RECNO interface.

       ·   Changed the default flags from O_RDWR to
           O_CREAT|O_RDWR and the default mode from 0640 to 0666.

       ·   Made DB_File automatically import the open() constants
           (O_RDWR, O_CREAT etc.) from Fcntl, if available.

       ·   Updated documentation.

       Refer to the HISTORY section in DB_File.pm for a complete
       list of changes. Everything after DB_File 1.01 has been
       added since 5.003.

       Net::Ping

       Major rewrite - support added for both udp echo and real
       icmp pings.

       Object-oriented overrides for builtin operators

       Many of the Perl builtins returning lists now have object-
       oriented overrides.  These are:

           File::stat
           Net::hostent
           Net::netent
           Net::protoent
           Net::servent

       Sends converted HTML to standard output
           The pod2html utility included with Perl 5.004 is
           entirely new.  By default, it sends the converted HTML
           to its standard output, instead of writing it to a
           file like Perl 5.003's pod2html did.  Use the --out­
           file=FILENAME option to write to a file.

       xsubpp

       "void" XSUBs now default to returning nothing
           Due to a documentation/implementation bug in previous
           versions of Perl, XSUBs with a return type of "void"
           have actually been returning one value.  Usually that
           value was the GV for the XSUB, but sometimes it was
           some already freed or reused value, which would some­
           times lead to program failure.

           In Perl 5.004, if an XSUB is declared as returning
           "void", it actually returns no value, i.e. an empty
           list (though there is a backward-compatibility excep­
           tion; see below).  If your XSUB really does return an
           SV, you should give it a return type of "SV *".

           For backward compatibility, xsubpp tries to guess
           whether a "void" XSUB is really "void" or if it wants
           to return an "SV *".  It does so by examining the text
           of the XSUB: if xsubpp finds what looks like an
           assignment to ST(0), it assumes that the XSUB's return
           type is really "SV *".


C Language API Changes

       "gv_fetchmethod" and "perl_call_sv"
           The "gv_fetchmethod" function finds a method for an
           object, just like in Perl 5.003.  The GV it returns
           may be a method cache entry.  However, in Perl 5.004,
           method cache entries are not visible to users; there­
           fore, they can no longer be passed directly to
           "perl_call_sv".  Instead, you should use the "GvCV"
           macro on the GV to extract its CV, and pass the CV to
           "perl_call_sv".

           The most likely symptom of passing the result of
           "gv_fetchmethod" to "perl_call_sv" is Perl's producing
           an "Undefined subroutine called" error on the second
           call to a given method (since there is no cache on the
           first call).

       "perl_eval_pv"
           A new function handy for eval'ing strings of Perl code
           inside C code.  This function returns the value from
           (hash entries), which can be more efficient.  See
           perlguts for details.


Documentation Changes

       Many of the base and library pods were updated.  These new
       pods are included in section 1:

       perldelta
           This document.

       perlfaq
           Frequently asked questions.

       perllocale
           Locale support (internationalization and localiza­
           tion).

       perltoot
           Tutorial on Perl OO programming.

       perlapio
           Perl internal IO abstraction interface.

       perlmodlib
           Perl module library and recommended practice for mod­
           ule creation.  Extracted from perlmod (which is much
           smaller as a result).

       perldebug
           Although not new, this has been massively updated.

       perlsec
           Although not new, this has been massively updated.


New Diagnostics

       Several new conditions will trigger warnings that were
       silent before.  Some only affect certain platforms.  The
       following new warnings and errors outline these.  These
       messages are classified as follows (listed in increasing
       order of desperation):

          (W) A warning (optional).
          (D) A deprecation (optional).
          (S) A severe warning (mandatory).
          (F) A fatal error (trappable).
          (P) An internal error you should never see (trappable).
          (X) A very fatal error (nontrappable).
          (A) An alien error message (not generated by Perl).

       "my" variable %s masks earlier declaration in same scope
           (W) A lexical variable has been redeclared in the same
           scope, effectively eliminating all access to the pre­
               @foo{$bar, $baz, $xyzzy}
               @{$ref->[12]}{"susie", "queue"}

       Allocation too large: %lx
           (X) You can't allocate more than 64K on an MS-DOS
           machine.

       Allocation too large
           (F) You can't allocate more than 2^31+"small amount"
           bytes.

       Applying %s to %s will act on scalar(%s)
           (W) The pattern match (//), substitution (s///), and
           transliteration (tr///) operators work on scalar val­
           ues.  If you apply one of them to an array or a hash,
           it will convert the array or hash to a scalar value --
           the length of an array, or the population info of a
           hash -- and then work on that scalar value.  This is
           probably not what you meant to do.  See "grep" in
           perlfunc and "map" in perlfunc for alternatives.

       Attempt to free nonexistent shared string
           (P) Perl maintains a reference counted internal table
           of strings to optimize the storage and access of hash
           keys and other strings.  This indicates someone tried
           to decrement the reference count of a string that can
           no longer be found in the table.

       Attempt to use reference as lvalue in substr
           (W) You supplied a reference as the first argument to
           substr() used as an lvalue, which is pretty strange.
           Perhaps you forgot to dereference it first.  See "sub­
           str" in perlfunc.

       Bareword "%s" refers to nonexistent package
           (W) You used a qualified bareword of the form "Foo::",
           but the compiler saw no other uses of that namespace
           before that point.  Perhaps you need to predeclare a
           package?

       Can't redefine active sort subroutine %s
           (F) Perl optimizes the internal handling of sort sub­
           routines and keeps pointers into them.  You tried to
           redefine one such sort subroutine when it was cur­
           rently active, which is not allowed.  If you really
           want to do this, you should write "sort { &func } @x"
           instead of "sort func @x".

       Can't use bareword ("%s") as %s ref while "strict refs" in
       use
           (F) Only hard references are allowed by "strict refs".
           Symbolic references are disallowed.  See perlref.
           been eligible for inlining.  See "Constant Functions"
           in perlsub for commentary and workarounds.

       Copy method did not return a reference
           (F) The method which overloads "=" is buggy. See "Copy
           Constructor" in overload.

       Died
           (F) You passed die() an empty string (the equivalent
           of "die """) or you called it with no args and both $@
           and $_ were empty.

       Exiting pseudo-block via %s
           (W) You are exiting a rather special block construct
           (like a sort block or subroutine) by unconventional
           means, such as a goto, or a loop control statement.
           See "sort" in perlfunc.

       Identifier too long
           (F) Perl limits identifiers (names for variables,
           functions, etc.) to 252 characters for simple names,
           somewhat more for compound names (like $A::B).  You've
           exceeded Perl's limits.  Future versions of Perl are
           likely to eliminate these arbitrary limitations.

       Illegal character %s (carriage return)
           (F) A carriage return character was found in the
           input.  This is an error, and not a warning, because
           carriage return characters can break multi-line
           strings, including here documents (e.g., "print
           <<EOF;").

       Illegal switch in PERL5OPT: %s
           (X) The PERL5OPT environment variable may only be used
           to set the following switches: -[DIMUdmw].

       Integer overflow in hex number
           (S) The literal hex number you have specified is too
           big for your architecture. On a 32-bit architecture
           the largest hex literal is 0xFFFFFFFF.

       Integer overflow in octal number
           (S) The literal octal number you have specified is too
           big for your architecture. On a 32-bit architecture
           the largest octal literal is 037777777777.

       internal error: glob failed
           (P) Something went wrong with the external program(s)
           used for "glob" and "<*.c>".  This may mean that your
           csh (C shell) is broken.  If so, you should change all
           of the csh-related variables in config.sh:  If you
           have tcsh, make the variables refer to it as if it

       Invalid type in unpack: '%s'
           (F) The given character is not a valid unpack type.
           See "unpack" in perlfunc.

       Name "%s::%s" used only once: possible typo
           (W) Typographical errors often show up as unique vari­
           able names.  If you had a good reason for having a
           unique name, then just mention it again somehow to
           suppress the message (the "use vars" pragma is pro­
           vided for just this purpose).

       Null picture in formline
           (F) The first argument to formline must be a valid
           format picture specification.  It was found to be
           empty, which probably means you supplied it an unini­
           tialized value.  See perlform.

       Offset outside string
           (F) You tried to do a read/write/send/recv operation
           with an offset pointing outside the buffer.  This is
           difficult to imagine.  The sole exception to this is
           that "sysread()"ing past the buffer will extend the
           buffer and zero pad the new area.

       Out of memory!
           (X|F) The malloc() function returned 0, indicating
           there was insufficient remaining memory (or virtual
           memory) to satisfy the request.

           The request was judged to be small, so the possibility
           to trap it depends on the way Perl was compiled.  By
           default it is not trappable.  However, if compiled for
           this, Perl may use the contents of $^M as an emergency
           pool after die()ing with this message.  In this case
           the error is trappable once.

       Out of memory during request for %s
           (F) The malloc() function returned 0, indicating there
           was insufficient remaining memory (or virtual memory)
           to satisfy the request. However, the request was
           judged large enough (compile-time default is 64K), so
           a possibility to shut down by trapping this error is
           granted.

       panic: frexp
           (P) The library function frexp() failed, making
           printf("%f") impossible.

       Possible attempt to put comments in qw() list
           (W) qw() lists contain items separated by whitespace;
           as with literal strings, comment characters are not
           ignored, but are instead treated as literal data.
               @list = qw(
                   a
                   b
               );

           If you really want comments, build your list the old-
           fashioned way, with quotes and commas:

               @list = (
                   'a',    # a comment
                   'b',    # another comment
               );

       Possible attempt to separate words with commas
           (W) qw() lists contain items separated by whitespace;
           therefore commas aren't needed to separate the items.
           (You may have used different delimiters than the
           parentheses shown here; braces are also frequently
           used.)

           You probably wrote something like this:

               qw! a, b, c !;

           which puts literal commas into some of the list items.
           Write it without commas if you don't want them to
           appear in your data:

               qw! a b c !;

       Scalar value @%s{%s} better written as $%s{%s}
           (W) You've used a hash slice (indicated by @) to
           select a single element of a hash.  Generally it's
           better to ask for a scalar value (indicated by $).
           The difference is that $foo{&bar} always behaves like
           a scalar, both when assigning to it and when evaluat­
           ing its argument, while @foo{&bar} behaves like a list
           when you assign to it, and provides a list context to
           its subscript, which can do weird things if you're
           expecting only one subscript.

       Stub found while resolving method `%s' overloading `%s' in
       %s
           (P) Overloading resolution over @ISA tree may be bro­
           ken by importing stubs.  Stubs should never be implic­
           itly created, but explicit calls to "can" may break
           this.

       Too late for "-T" option
           (X) The #! line (or local equivalent) in a Perl script
           contains the -T option, but Perl was not invoked with
           -T in its argument list.  This is an error because, by

       Unsupported function fork
           (F) Your version of executable does not support fork­
           ing.

           Note that under some systems, like OS/2, there may be
           different flavors of Perl executables, some of which
           may support fork, some not. Try changing the name you
           call Perl by to "perl_", "perl__", and so on.

       Use of "$$<digit>" to mean "${$}<digit>" is deprecated
           (D) Perl versions before 5.004 misinterpreted any type
           marker followed by "$" and a digit.  For example,
           "$$0" was incorrectly taken to mean "${$}0" instead of
           "${$0}".  This bug is (mostly) fixed in Perl 5.004.

           However, the developers of Perl 5.004 could not fix
           this bug completely, because at least two widely-used
           modules depend on the old meaning of "$$0" in a
           string.  So Perl 5.004 still interprets "$$<digit>" in
           the old (broken) way inside strings; but it generates
           this message as a warning.  And in Perl 5.005, this
           special treatment will cease.

       Value of %s can be "0"; test with defined()
           (W) In a conditional expression, you used <HANDLE>,
           <*> (glob), "each()", or "readdir()" as a boolean
           value.  Each of these constructs can return a value of
           "0"; that would make the conditional expression false,
           which is probably not what you intended.  When using
           these constructs in conditional expressions, test
           their values with the "defined" operator.

       Variable "%s" may be unavailable
           (W) An inner (nested) anonymous subroutine is inside a
           named subroutine, and outside that is another subrou­
           tine; and the anonymous (innermost) subroutine is ref­
           erencing a lexical variable defined in the outermost
           subroutine.  For example:

              sub outermost { my $a; sub middle { sub { $a } } }

           If the anonymous subroutine is called or referenced
           (directly or indirectly) from the outermost subrou­
           tine, it will share the variable as you would expect.
           But if the anonymous subroutine is called or refer­
           enced when the outermost subroutine is not active, it
           will see the value of the shared variable as it was
           before and during the *first* call to the outermost
           subroutine, which is probably not what you want.

           In these circumstances, it is usually best to make the
           middle subroutine anonymous, using the "sub {}" syn­
           variable.  In other words, the variable will no longer
           be shared.

           Furthermore, if the outer subroutine is anonymous and
           references a lexical variable outside itself, then the
           outer and inner subroutines will never share the given
           variable.

           This problem can usually be solved by making the inner
           subroutine anonymous, using the "sub {}" syntax.  When
           inner anonymous subs that reference variables in outer
           subroutines are called or referenced, they are auto­
           matically rebound to the current values of such vari­
           ables.

       Warning: something's wrong
           (W) You passed warn() an empty string (the equivalent
           of "warn """) or you called it with no args and $_ was
           empty.

       Ill-formed logical name |%s| in prime_env_iter
           (W) A warning peculiar to VMS.  A logical name was
           encountered when preparing to iterate over %ENV which
           violates the syntactic rules governing logical names.
           Since it cannot be translated normally, it is skipped,
           and will not appear in %ENV.  This may be a benign
           occurrence, as some software packages might directly
           modify logical name tables and introduce nonstandard
           names, or it may indicate that a logical name table
           has been corrupted.

       Got an error from DosAllocMem
           (P) An error peculiar to OS/2.  Most probably you're
           using an obsolete version of Perl, and this should not
           happen anyway.

       Malformed PERLLIB_PREFIX
           (F) An error peculiar to OS/2.  PERLLIB_PREFIX should
           be of the form

               prefix1;prefix2

           or

               prefix1 prefix2

           with nonempty prefix1 and prefix2.  If "prefix1" is
           indeed a prefix of a builtin library search path, pre­
           fix2 is substituted.  The error may appear if compo­
           nents are not found, or are too long.  See "PERL­
           LIB_PREFIX" in README.os2.

       If you find what you think is a bug, you might check the
       headers of recently posted articles in the
       comp.lang.perl.misc newsgroup.  There may also be informa­
       tion 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.  Make sure you
       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.com> to be analysed by the
       Perl porting team.


SEE ALSO

       The Changes file for exhaustive details on what changed.

       The INSTALL file for how to build Perl.  This file has
       been significantly updated for 5.004, so even veteran
       users should look through it.

       The README file for general stuff.

       The Copying file for copyright information.


HISTORY

       Constructed by Tom Christiansen, grabbing material with
       permission from innumerable contributors, with kibitzing
       by more than a few Perl porters.

       Last update: Wed May 14 11:14:09 EDT 1997

perl v5.8.1                 2003-09-02           PERL5004DELTA(1)

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