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PERL5004DELTA(1)       Perl Programmers Reference Guide       PERL5004DELTA(1)

       perl5004delta - whats new for perl5.004

       This document describes differences between the 5.003 release (as docu
       mented in Programming Perl, second edition--the Camel Book) and this

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 distribution 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 "Cant locate Foo.pm in @INC" error

       The error "Cant locate Foo.pm in @INC" now lists the contents 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 compatibil
       ity, 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 preserved 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 vari
       able as if its contents had appeared on a "#!perl" line at the begin
       ning 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"

       The -T option is also forbidden on the "#!" line of a script, unless it
       was present on the Perl command line.  Due to the way "#!"  works, this
       usually means that -T must be in the first argument.  Thus:

	   #!/usr/bin/perl -T -w

       will probably work for an executable script invoked as "scriptname",

	   #!/usr/bin/perl -w -T

       will probably fail under the same conditions.  (Non-Unix systems will
       probably not follow this rule.)	But "perl scriptname" is guaranteed to
       fail, since then there is no 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 warnings, 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.	How
       ever, 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", execute "*AUTOLOAD = \&BaseClass::AUTOLOAD" during

       Previously deprecated %OVERLOAD is no longer usable

       Using %OVERLOAD to define overloading was deprecated in 5.003.  Over
       loading 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 theyre 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).  Earlier
       versions of Perl never brought them into existence.

       For example, given this code:

	    undef @a; undef %a;
	    sub show { print $_[0] };
	    sub change { $_[0]++ };

       After this code executes in Perl 5.004, $a{b} exists but $a[2] does
       not.  In Perl 5.002 and 5.003, both $a{b} and $a[2] would have existed
       (but $a[2]s value would have been undefined).

       Group vector changeable with $)

       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 "set
       groups()" C function 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 $$, &$, 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 com
       pletely, because at least two widely-used modules depend on the old
       meaning of "$$0" in a string.  So Perl 5.004 still interprets
       "$$" 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.

       Fixed localization of $, $&, etc.

       Perl versions before 5.004 did not always properly localize the regex-
       related special variables.  Perl 5.004 does localize them, as the docu
       mentation 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 circumstance; 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 subroutines return value will not
       be used at all, which allows subroutines to avoid a time-consuming cal
       culation of a return value if it isnt going to be used.

       "eval EXPR" determines value of EXPR in scalar context

       Perl (version 5) used to determine the value of EXPR inconsistently,
       sometimes incorrectly using the surrounding context for the determina
       tion.  Now, the value of EXPR (before being parsed by eval) is always
       determined in a scalar context.	Once parsed, it is executed as before,
       by providing the context that the scope surrounding the eval provided.
       This change makes the behavior Perl4 compatible, besides fixing bugs
       resulting from the inconsistent behavior.  This program:

	   @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 con
       ditions 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 its unlikely, this may cause a
       previously-working script to now fail -- which should be construed 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 implemented without the use of an external pro

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

       No spawning if tainted $TERM doesnt 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 metacharacters 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 imple
       mented using the new Opcode module.  Please read the new Opcode and
       Safe documentation.

       Embedding improvements

       In older versions of Perl it was not possible to create more than one
       Perl interpreter instance inside a single process without leaking like
       a sieve and/or crashing.  The bugs that caused this behavior have all
       been fixed.  However, you still must take care when embedding Perl in a
       C program.  See the updated perlembed manpage for tips on how to manage
       your interpreters.

       Internal change: FileHandle class based on IO::* classes

       File handles are now stored internally as type IO::Handle.  The File
       Handle module is still supported for backwards compatibility, but it is
       now merely a front end to the IO::* modules -- specifically, IO::Han
       dle, IO::Seekable, 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&Ts sfio IO package instead of
       stdio.  See perlapio for more details, and the INSTALL file for how to
       use it.

       New and changed syntax

	   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($foo)" as "$sub
	   ref->($foo)".  All these arrow terms may be chained; thus, "&{$ta
	   ble->{FOO}}($bar)" may now be written "$table->{FOO}->($bar)".

       New and changed builtin constants

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

       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 vari

       $^M By default, running out of memory 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.  Suppose that your Perl were
	   compiled with -DPERL_EMERGENCY_SBRK and used Perls malloc.  Then

	       $^M = a x (1<<16);

	   would allocate a 64K buffer for use when in emergency.  See the
	   INSTALL file for information on how to enable this option.  As a
	   disincentive to casual use of this advanced feature, there is no
	   "use English" long name for this variable.

       New and changed builtin functions

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

	   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 doesnt use the C
	   library function sprintf() any more, except for floating-point num
	   bers, 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 Perls 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 conversion are:

	      #    prefix octal with "0", hex with "0x"
	      h    interpret integer as C type "short" or "unsigned short"
	      V    interpret integer as Perls 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 conversion and

       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

	       keys %hash = 200;

	   then %hash will have at least 200 buckets allocated for it.	These
	   buckets will be retained even if you do "%hash = ()"; use "undef
	   %hash" if you want to free the storage while %hash is still in
	   scope.  You cant shrink the number of buckets allocated for the
	   hash using "keys" in this way (but you neednt worry about doing
	   this by accident, as trying has no effect).

       my() in Control Structures
	   You can now use my() (with or without the parentheses) in the con
	   trol expressions of control structures such as:

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

	       if ((my $answer = ) =~ /^y(es)?$/i) {
	       } elsif ($answer =~ /^n(o)?$/i) {
	       } 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) {

	   $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 punctuation 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 signif
	   icant 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 generate a NULL

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

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

       use VERSION
	   If the first argument to "use" is a number, it is treated as a ver
	   sion number instead of a module name.  If the version of the Perl
	   interpreter is less than VERSION, then an error message is printed
	   and Perl exits immediately.	Because "use" occurs at compile time,
	   this check happens immediately during the compilation process,
	   unlike "require VERSION", which waits until runtime for the check.
	   This is often useful if you need to check the current Perl version
	   before "use"ing library modules which have changed in incompatible
	   ways from older versions of Perl.  (We try not to do this more than
	   we have to.)

       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, inher
	   ited from the UNIVERSAL 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 dont use the Exporter.	It is the recommended method
	   for new code.

	   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 actu
	   ally new; just never documented before.)

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

	   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 youre calling "rand" and
	   havent 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
	   strings search position (which is visible through the "pos" opera
	   tor) 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 "con
	   tinue") modifier, i.e. "m//gc".  This feature, in conjunction with
	   the "\G" zero-width assertion, makes it possible to chain matches
	   together.  See perlop and perlre.

       "m//x" ignores whitespace before ?*+{}
	   The "m//x" construct has always been intended to ignore all
	   unescaped whitespace.  However, before Perl 5.004, whitespace had
	   the effect of escaping repeat modifiers like "*" or "?"; for exam
	   ple, "/a *b/x" was (mis)interpreted as "/a\*b/x".  This bug has
	   been fixed in 5.004.

       nested "sub{}" closures work now
	   Prior to the 5.004 release, nested anonymous functions didnt work
	   right.  They do now.

       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), for
	   mats now work properly.  For example, this silently failed before
	   (printed only zeros), but is fine now:

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

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

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

       New builtin methods

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

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

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

	       use UNIVERSAL qw(isa);

	       if(isa($ref, ARRAY)) {

	   "can" checks to see if its object has a method called "METHOD", if
	   it does then a reference to the sub is returned; if it does not
	   then undef is returned.

       VERSION( [NEED] )
	   "VERSION" returns the version number of the class (package).  If
	   the NEED argument is given then it will check that the current ver
	   sion (as defined by the $VERSION variable in the given package) not
	   less than NEED; it will die if this is not the case.  This method
	   is normally called as a class method.  This method is called auto
	   matically by the "VERSION" form of "use".

	       use A 1.2 qw(some imported subs);
	       # implies:

       NOTE: "can" directly uses Perls 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 pack

       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 reference can be used to hold
	   some internal information.

	       sub TIEHANDLE {
		   print "\n";
		   my $i;
		   return bless \$i, shift;

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

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

       PRINTF this, LIST
	   This method will be triggered every time the tied handle 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 {
		     my $fmt = shift;
		   print sprintf($fmt, @_)."\n";

       READ this LIST
	   This method will be called when the handle is read from via the
	   "read" or "sysread" functions.

	       sub READ {
		   $r = shift;
		   my($buf,$len,$offset) = @_;
		   print "READ called, \$buf=$buf, \$len=$len, \$offset=$offset";

       READLINE this
	   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 "Dont 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 debug
	   ging and possibly for cleaning up.

	       sub DESTROY {
		   print "\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 mem
       ory 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, youll 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 malloc().)

	   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".

	   Perl memory allocation is by bucket with sizes close to powers of
	   two.  Because of these malloc overhead may be big, especially for
	   data of size exactly a power of two.  If "PACK_MALLOC" is defined,
	   perl uses a slightly different algorithm for small allocations (up
	   to 64 bytes long), which makes it possible to have overhead down to
	   1 byte for allocations which are powers of two (and appear quite

	   Expected memory savings (with 8-byte alignment in "alignbytes") is
	   about 20% for typical Perl usage.  Expected slowdown due to addi
	   tional malloc overhead is in fractions of a percent (hard to mea
	   sure, because of the effect of saved memory on speed).

	   Similarly to "PACK_MALLOC", this macro improves allocations 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 processing.

	   On recent systems, the fact that perl requires 2M from system for
	   1M allocation will not affect speed of execution, 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 applications which
	   require most memory in such 2**n chunks); expected slowdown is neg

       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.


       Perl 5.004 now includes support for building a "native" perl under Win
       dows NT, using the Microsoft Visual C++ compiler (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 environment.
       Cygwin32 is a set of GNU tools that make it possible to compile and run
       many Unix programs under Windows NT by providing a mostly Unix-like
       interface for compilation and execution.  See README.cygwin32 in the
       perl distribution for more details on this port and how to obtain the
       Cygwin32 toolkit.

       Plan 9

       See README.plan9 in the perl distribution.


       See README.qnx in the perl distribution.


       See README.amigaos in the perl distribution.

       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 MODULE).  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

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

       use constant NAME => VALUE
	   Provides a convenient interface for creating compile-time con
	   stants, 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 mapping; 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::set

	   See perllocale for more information.

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

       use vmsish
	   Enable VMS-specific language features.  Currently, there are three
	   VMS-specific features available: status, which makes $? and "sys
	   tem" return genuine VMS status values instead of emulating POSIX;
	   exit, which makes "exit" take a genuine VMS status value instead
	   of assuming that "exit 1" is an error; and time, which makes all
	   times relative to the local time zone, in the VMS tradition.

       Required Updates

       Though Perl 5.004 is compatible with almost all modules that work with
       Perl 5.003, there are a few exceptions:

	   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, doesnt work
       with Perl 5.004 (nor with perl 4), because it executes an invalid regu
       lar 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 directory, which is where the
       shared libraries for extensions have always been.  This change is
       intended to allow administrators to keep the Perl 5.004 library direc
       tory unchanged from a previous version, without running the risk of
       binary incompatibility between extensions Perl source and shared

       Module information summary

       Brand new modules, arranged by topic rather than strictly alphabeti

	   CGI.pm		Web server interface ("Common Gateway Interface")
	   CGI/Apache.pm	Support for Apaches 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

	   FindBin.pm		Find path of currently executing program

	   Class/Struct.pm	Declare struct-like datatypes as Perl classes
	   File/stat.pm 	By-name interface to Perls builtin stat
	   Net/hostent.pm	By-name interface to Perls builtin gethost*
	   Net/netent.pm	By-name interface to Perls builtin getnet*
	   Net/protoent.pm	By-name interface to Perls builtin getproto*
	   Net/servent.pm	By-name interface to Perls builtin getserv*
	   Time/gmtime.pm	By-name interface to Perls builtin gmtime
	   Time/localtime.pm	By-name interface to Perls builtin localtime
	   Time/tm.pm		Internal object for Time::{gm,local}time
	   User/grent.pm	By-name interface to Perls builtin getgr*
	   User/pwent.pm	By-name interface to Perls builtin getpw*

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

	   UNIVERSAL.pm 	Base class for *ALL* classes


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


       These constants are intended for use with the Perl operators 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 systems documentation for fcntl() and open().

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


       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").


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


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


       The Math::Complex module has been totally rewritten, and now supports
       more operations.  These are overloaded:

	    + - * / ** <=> neg ~ abs sqrt exp log sin cos atan2 "" (stringify)

       And these functions are now exported:

	   pi i Re Im arg
	   log10 logn ln cbrt root
	   csc sec cot
	   asin acos atan
	   acsc asec acot
	   sinh cosh tanh
	   csch sech coth
	   asinh acosh atanh
	   acsch asech acoth
	   cplx cplxe


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


       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

	  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.


       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:


       For example, you can now say

	   use File::stat;
	   use User::pwent;
	   $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid);

Utility Changes

       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 5.003s pod2html did.
	   Use the --outfile=FILENAME option to write to a file.


       "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 return
	   ing one value.  Usually that value was the GV for the XSUB, but
	   sometimes it was some already freed or reused value, which would
	   sometimes lead to program failure.

	   In Perl 5.004, if an XSUB is declared as returning "void", it actu
	   ally returns no value, i.e. an empty list (though there is a back
	   ward-compatibility exception; 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 XSUBs 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; therefore, 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 Perls producing an "Undefined subroutine
	   called" error on the second call to a given method (since there is
	   no cache on the first call).

	   A new function handy for evaling strings of Perl code inside C
	   code.  This function returns the value from the eval statement,
	   which can be used instead of fetching globals from the symbol ta
	   ble.  See perlguts, perlembed and perlcall for details and exam

       Extended API for manipulating hashes
	   Internal handling of hash keys has changed.	The old hashtable API
	   is still fully supported, and will likely remain so.  The additions
	   to the API allow passing keys as "SV*"s, so that "tied" hashes can
	   be given real scalars as keys rather than plain strings (nontied
	   hashes still can only use strings as keys).	New extensions must
	   use the new hash access functions and macros if they wish to use
	   "SV*" keys.	These additions also make it feasible to manipulate
	   "HE*"s (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:

	   This document.

	   Frequently asked questions.

	   Locale support (internationalization and localization).

	   Tutorial on Perl OO programming.

	   Perl internal IO abstraction interface.

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

	   Although not new, this has been massively updated.

	   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 previous instance.  This
	   is almost always a typographical error.  Note that the earlier
	   variable will still exist until the end of the scope or until all
	   closure referents to it are destroyed.

       %s argument is not a HASH element or slice
	   (F) The argument to delete() must be either a hash element, such as


	   or a hash slice, such as

	       @foo{$bar, $baz, $xyzzy}
	       @{$ref->[12]}{"susie", "queue"}

       Allocation too large: %lx
	   (X) You cant allocate more than 64K on an MS-DOS machine.

       Allocation too large
	   (F) You cant allocate more than 2^31+"small amount" bytes.

       Applying %s to %s will act on scalar(%s)
	   (W) The pattern match (//), substitution (s///), and translitera
	   tion (tr///) operators work on scalar values.  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 "substr" in perlfunc.

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

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

       Cant 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.

       Cannot resolve method %s overloading %s in package %s
	   (P) Internal error trying to resolve overloading specified by a
	   method name (as opposed to a subroutine reference).

       Constant subroutine %s redefined
	   (S) You redefined a subroutine which had previously been eligible
	   for inlining.  See "Constant Functions" in perlsub for commentary
	   and workarounds.

       Constant subroutine %s undefined
	   (S) You undefined a subroutine which had previously 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.

	   (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).	Youve exceeded Perls limits.  Future ver
	   sions 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
	   <".	This may mean that your csh (C shell) is bro
	   ken.  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 were csh (e.g. "full_csh=/usr/bin/tcsh"); otherwise, make them
	   all empty (except that "d_csh" should be undef) so that Perl will
	   think csh is missing.  In either case, after editing config.sh, run
	   "./Configure -S" and rebuild Perl.

       Invalid conversion in %s: "%s"
	   (W) Perl does not understand the given format conversion.  See
	   "sprintf" in perlfunc.

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

       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 variable names.
	   If you had a good reason for having a unique name, then just men
	   tion it again somehow to suppress the message (the "use vars"
	   pragma is provided 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 uninitialized 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 insuf
	   ficient remaining memory (or virtual memory) to satisfy the

	   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 trap
	   pable.  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 insuffi
	   cient 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

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

       Possible attempt to put comments in qw() list
	   (W) qw() lists contain items separated by whitespace; as with lit
	   eral strings, comment characters are not ignored, but are instead
	   treated as literal data.  (You may have used different delimiters
	   than the parentheses shown here; braces are also frequently used.)

	   You probably wrote something like this:

	       @list = qw(
		   a # a comment
		   b # another comment

	   when you should have written this:

	       @list = qw(

	   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 arent needed to separate the items. (You may have used dif
	   ferent 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 dont want them to appear in your data:

	       qw! a b c !;

       Scalar value @%s{%s} better written as $%s{%s}
	   (W) Youve used a hash slice (indicated by @) to select a single
	   element of a hash.  Generally its 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 evaluating 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 youre expecting only one subscript.

       Stub found while resolving method %s overloading %s in %s
	   (P) Overloading resolution over @ISA tree may be broken by import
	   ing stubs.  Stubs should never be implicitly 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 the time Perl discovers a -T in a
	   script, its too late to properly taint everything from the envi
	   ronment.  So Perl gives up.

       untie attempted while %d inner references still exist
	   (W) A copy of the object returned from "tie" (or "tied") was still
	   valid when "untie" was called.

       Unrecognized character %s
	   (F) The Perl parser has no idea what to do with the specified char
	   acter in your Perl script (or eval).  Perhaps you tried to run a
	   compressed script, a binary program, or a directory as a Perl pro

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

	   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 "$$" to mean "${$}" is deprecated
	   (D) Perl versions before 5.004 misinterpreted any type marker fol
	   lowed by "$" and a digit.  For example, "$$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 com
	   pletely, because at least two widely-used modules depend on the old
	   meaning of "$$0" in a string.  So Perl 5.004 still interprets
	   "$$" in the old (broken) way inside strings; but it gener
	   ates 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 , <*> (glob),
	   "each()", or "readdir()" as a boolean value.  Each of these con
	   structs 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 val
	   ues with the "defined" operator.

       Variable "%s" may be unavailable
	   (W) An inner (nested) anonymous subroutine is inside a named sub
	   routine, and outside that is another subroutine; and the anonymous
	   (innermost) subroutine is referencing 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 subroutine, it will share the vari
	   able as you would expect.  But if the anonymous subroutine is
	   called or referenced 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 prob
	   ably not what you want.

	   In these circumstances, it is usually best to make the middle sub
	   routine anonymous, using the "sub {}" syntax.  Perl has specific
	   support for shared variables in nested anonymous subroutines; a
	   named subroutine in between interferes with this feature.

       Variable "%s" will not stay shared
	   (W) An inner (nested) named subroutine is referencing a lexical
	   variable defined in an outer subroutine.

	   When the inner subroutine is called, it will probably see the value
	   of the outer subroutines variable as it was before and during the
	   *first* call to the outer subroutine; in this case, after the first
	   call to the outer subroutine is complete, the inner and outer sub
	   routines will no longer share a common value for the 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 subrou
	   tines 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 refer
	   enced, they are automatically rebound to the current values of such

       Warning: somethings 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 youre using an obso
	   lete 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



	       prefix1 prefix2

	   with nonempty prefix1 and prefix2.  If "prefix1" is indeed a prefix
	   of a builtin library search path, prefix2 is substituted.  The
	   error may appear if components are not found, or are too long.  See

       PERL_SH_DIR too long
	   (F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find
	   the "sh"-shell in.  See "PERL_SH_DIR" in README.os2.

       Process terminated by SIG%s
	   (W) This is a standard message issued by OS/2 applications, while
	   *nix applications die in silence.  It is considered a feature of
	   the OS/2 port.  One can easily disable this by appropriate sighan
	   dlers, see "Signals" in perlipc.  See also "Process terminated by

       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 information at http://www.perl.com/perl/ , the Perl Home

       If you believe you have an unreported bug, please run the perlbug pro
       gram 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  to be analysed by
       the Perl porting team.

       The Changes file for exhaustive details on what changed.

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

       The README file for general stuff.

       The Copying file for copyright information.

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

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

perl v5.8.8			  2008-04-25		      PERL5004DELTA(1)

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