X-Git-Url: https://perl5.git.perl.org/perl5.git/blobdiff_plain/1e422769b80038b1bfc4f5af33438b87cc1c7a22..f7c603cbfba7c97f77e257c42aa119ffdb47fe1e:/pod/perldelta.pod

diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index bfdf903..bfa57c0 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -10,15 +10,23 @@ this one.
 
 =head1 Supported Environments
 
-Perl5.004 builds out of the box on Unix, Plan9, LynxOS, VMS, OS/2,
-QNX, and AmigaOS.
+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.
 
 =head1 Core Changes
 
-Most importantly, many bugs were fixed.  See the F<Changes>
-file in the distribution for details.
+Most importantly, many bugs were fixed, including several security
+problems.  See the F<Changes> file in the distribution for details.
 
-=head2 Compilation Option: Binary Compatibility With 5.003
+=head2 List assignment to %ENV works
+
+C<%ENV = ()> and C<%ENV = @list> now work as expected (except on VMS
+where it generates a fatal error).
+
+=head2 "Can't locate Foo.pm in @INC" error now lists @INC
+
+=head2 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
@@ -27,36 +35,235 @@ 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.
 
-=head2 New Opcode Module and Revised Safe Module
+=head2 $PERL5OPT environment variable
+
+You may now put Perl options in the $PERL5OPT environment variable.
+Unless Perl is running with taint checks, it will interpret this
+variable as if its contents had appeared on a "#!perl" line at the
+beginning of your script, except that hyphens are optional.  PERL5OPT
+may only be used to set the following switches: B<-[DIMUdmw]>.
+
+=head2 Limitations on B<-M>, B<-m>, and B<-T> options
+
+The C<-M> and C<-m> options are no longer allowed on the C<#!> line of
+a script.  If a script needs a module, it should invoke it with the
+C<use> pragma.
+
+The B<-T> option is also forbidden on the C<#!> line of a script,
+unless it was present on the Perl command line.  Due to the way C<#!>
+works, this usually means that B<-T> must be in the first argument.
+Thus:
+
+    #!/usr/bin/perl -T -w
+
+will probably work for an executable script invoked as C<scriptname>,
+while:
+
+    #!/usr/bin/perl -w -T
+
+will probably fail under the same conditions.  (Non-Unix systems will
+probably not follow this rule.)  But C<perl scriptname> is guaranteed
+to fail, since then there is no chance of B<-T> being found on the
+command line before it is found on the C<#!> line.
+
+=head2 More precise warnings
+
+If you removed the B<-w> option from your Perl 5.003 scripts because it
+made Perl too verbose, we recommend that you try putting it back when
+you upgrade to Perl 5.004.  Each new perl version tends to remove some
+undesirable warnings, while adding new warnings that may catch bugs in
+your scripts.
+
+=head2 Deprecated: Inherited C<AUTOLOAD> for non-methods
+
+Before Perl 5.004, C<AUTOLOAD> functions were looked up as methods
+(using the C<@ISA> hierarchy), even when the function to be autoloaded
+was called as a plain function (e.g. C<Foo::bar()>), not a method
+(e.g. C<Foo-E<gt>bar()> or C<$obj-E<gt>bar()>).
+
+Perl 5.005 will use method lookup only for methods' C<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 C<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 C<AUTOLOAD> for non-methods from a base class named
+C<BaseClass>, execute C<*AUTOLOAD = \&BaseClass::AUTOLOAD> during startup.
+
+=head2 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
+L<overload> for more details.
+
+=head2 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 C<@_>).
+
+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 { $_[0]++ };
+     show($a[2]);
+     change($a{b});
+
+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 $a[2]'s value would have been undefined).
+
+=head2 Group vector changeable with C<$)>
+
+The C<$)> special variable has always (well, in Perl 5, at least)
+reflected not only the current effective group, but also the group list
+as returned by the C<getgroups()> C function (if there is one).
+However, until this release, there has not been a way to call the
+C<setgroups()> C function from Perl.
+
+In Perl 5.004, assigning to C<$)> 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
+C<setgroups()> C function (if there is one).
+
+=head2 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
+warning.  And in Perl 5.005, this special treatment will cease.
+
+=head2 No resetting of $. on implicit close
+
+The documentation for Perl 5.0 has always stated that C<$.> is I<not>
+reset when an already-open file handle is reopened with no intervening
+call to C<close>.  Due to a bug, perl versions 5.000 through 5.003
+I<did> reset C<$.> under that circumstance; Perl 5.004 does not.
+
+=head2 C<wantarray> may return undef
+
+The C<wantarray> operator returns true if a subroutine is expected to
+return a list, and false otherwise.  In Perl 5.004, C<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 of a return value if it isn't going to be used.
+
+=head2 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
+C<-T> invocation option.)  Although it's 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:
+
+=over
+
+=item 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 program.
+
+=item No spawning if tainted $CDPATH, $ENV, $BASH_ENV
+
+These environment variables may alter the behavior of spawned programs
+(especially shells) in ways that subvert security.  So now they are
+treated as dangerous, in the manner of $IFS and $PATH.
+
+=item 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
+metacharacters can cause trouble in $TERM.  So a tainted $TERM is
+considered to be safe if it contains only alphanumerics, underscores,
+dashes, and colons, and unsafe if it contains other characters (including
+whitespace).
+
+=back
+
+=head2 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 module.  Please read the new
 Opcode and Safe documentation.
 
-=head2 Fixed Parsing of $$<digit>, &$<digit>, etc.
+=head2 Embedding improvements
 
-A bug in previous versions of Perl 5.0 prevented proper parsing of
-numeric special variables as symbolic references.  That bug has been
-fixed.  As a result, the string "$$0" is no longer equivalent to
-C<$$."0">, but rather to C<${$0}>.  To get the old behavior, change
-"$$" followed by a digit to "${$}".
+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.
 
-=head2 Internal Change: FileHandle Deprecated
+=head2 Internal change: FileHandle class based on IO::* classes
 
-Filehandles are now stored internally as type IO::Handle.
-Although C<use FileHandle> and C<*STDOUT{FILEHANDLE}>
-are still supported for backwards compatibility,
-C<use IO::Handle> (or C<IO::Seekable> or C<IO::File>) and
-C<*STDOUT{IO}> are the way of the future.
+File handles are now stored internally as type IO::Handle.  The
+FileHandle module is still supported for backwards compatibility, but
+it is now merely a front end to the IO::* modules -- specifically,
+IO::Handle, IO::Seekable, and IO::File.  We suggest, but do not
+require, that you use the IO::* modules in new code.
 
-=head2 Internal Change: PerlIO internal IO abstraction interface
+In harmony with this change, C<*GLOB{FILEHANDLE}> is now just a
+backward-compatible synonym for C<*GLOB{IO}>.
+
+=head2 Internal change: PerlIO abstraction interface
 
 It is now possible to build Perl with AT&T's sfio IO package
 instead of stdio.  See L<perlapio> for more details, and
 the F<INSTALL> file for how to use it.
 
-=head2 New and Changed Built-in Variables
+=head2 New and changed syntax
+
+=over
+
+=item $coderef->(PARAMS)
+
+A subroutine reference may now be suffixed with an arrow and a
+(possibly empty) parameter list.  This syntax denotes a call of the
+referenced subroutine, with the given parameters (if any).
+
+This new syntax follows the pattern of S<C<$hashref-E<gt>{FOO}>> and
+S<C<$aryref-E<gt>[$foo]>>: You may now write S<C<&$subref($foo)>> as
+S<C<$subref-E<gt>($foo)>>.  All of these arrow terms may be chained;
+thus, S<C<&{$table-E<gt>{FOO}}($bar)>> may now be written
+S<C<$table-E<gt>{FOO}-E<gt>($bar)>>.
+
+=back
+
+=head2 New and changed builtin constants
+
+=over
+
+=item __PACKAGE__
+
+The current package name at compile time, or the undefined value if
+there is no current package (due to a C<package;> directive).  Like
+C<__FILE__> and C<__LINE__>, C<__PACKAGE__> does I<not> interpolate
+into strings.
+
+=back
+
+=head2 New and changed builtin variables
 
 =over
 
@@ -89,7 +296,7 @@ there is no C<use English> long name for this variable.
 
 =back
 
-=head2 New and Changed Built-in Functions
+=head2 New and changed builtin functions
 
 =over
 
@@ -99,14 +306,37 @@ This now works.  (e.g. C<delete @ENV{'PATH', 'MANPATH'}>)
 
 =item flock
 
-is now supported on more platforms, and prefers fcntl
-to lockf when emulating.
+is now supported on more platforms, prefers fcntl to lockf when
+emulating, and always flushes before (un)locking.
 
 =item printf and sprintf
 
-now support "%i" as a synonym for "%d", and the "h" modifier.
-So "%hi" means "short integer in decimal", and "%ho" means
-"unsigned short integer as octal".
+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 C<%> 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 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 L<perlfunc/sprintf> for a complete list of conversion and flags.
 
 =item keys as an lvalue
 
@@ -157,7 +387,7 @@ the loop, but not beyond it.
 Note that you still cannot use my() on global punctuation variables
 such as $_ and the like.
 
-=item unpack() and pack()
+=item 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
@@ -165,6 +395,16 @@ 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.
 
+Both pack() and unpack() now fail when their templates contain invalid
+types.  (Invalid types used to be ignored.)
+
+=item 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 reliable way to seek before using sysread() or syswrite().  Its
+return value is the new position, or the undefined value on failure.
+
 =item use VERSION
 
 If the first argument to C<use> is a number, it is treated as a version
@@ -172,7 +412,7 @@ 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 C<use> occurs at compile time, this check happens
 immediately during the compilation process, unlike C<require VERSION>,
-which waits until run-time for the check.  This is often useful if you
+which waits until runtime for the check.  This is often useful if you
 need to check the current Perl version before C<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.)
@@ -182,7 +422,7 @@ which have changed in incompatible ways from older versions of Perl.
 If the VERSION argument is present between Module and LIST, then the
 C<use> will call the VERSION method in class Module with the given
 version as an argument.  The default VERSION method, inherited from
-the Universal class, croaks if the given version is larger than the
+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!)
 
@@ -198,45 +438,66 @@ 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.)
 
+=item srand
+
+The default seed for C<srand>, which used to be C<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 C<rand> without first calling C<srand>
+would yield the same sequence of random numbers on most or all machines.
+Now, when perl sees that you're calling C<rand> and haven't yet called
+C<srand>, it calls C<srand> with the default seed. You should still call
+C<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.
+
 =item $_ as Default
 
 Functions documented in the Camel to default to $_ now in
 fact do, and all those that do are so documented in L<perlfunc>.
 
-=item C<m//g> does not trigger a pos() reset on failure
+=item C<m//gc> does not reset search position on failure
+
+The C<m//g> match iteration construct has always reset its target
+string's search position (which is visible through the C<pos> operator)
+when a match fails; as a result, the next C<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. C<m//gc>.  This feature, in conjunction with the C<\G> zero-width
+assertion, makes it possible to chain matches together.  See L<perlop>
+and L<perlre>.
 
-The C<m//g> match iteration construct used to reset the iteration
-when it failed to match (so that the next C<m//g> match would start at
-the beginning of the string).  You now have to explicitly do a
-C<pos $str = 0;> to reset the "last match" position, or modify the
-string in some way.  This change makes it practical to chain C<m//g>
-matches together in conjunction with ordinary matches using the C<\G>
-zero-width assertion.  See L<perlop> and L<perlre>.
+=item C<m//x> ignores whitespace before ?*+{}
+
+The C<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 example, C</a *b/x> was
+(mis)interpreted as C</a\*b/x>.  This bug has been fixed in 5.004.
 
 =item nested C<sub{}> closures work now
 
-Prior to the 5.004 release, nested anonymous functions 
-didn't work right.  They do now.
+Prior to the 5.004 release, nested anonymous functions didn't work
+right.  They do now.
 
 =item formats work right on changing lexicals
 
 Just like anonymous functions that contain lexical variables
 that change (like a lexical index variable for a C<foreach> loop),
 formats now work properly.  For example, this silently failed
-before, and is fine now:
+before (printed only zeros), but is fine now:
 
     my $i;
     foreach $i ( 1 .. 10 ) {
-	format =
+	write;
+    }
+    format =
 	my i is @#
 	$i
     .
-	write;
-    } 
 
 =back
 
-=head2 New Built-in Methods
+=head2 New builtin methods
 
 The C<UNIVERSAL> package automatically contains the following methods that
 are inherited by all other classes:
@@ -245,7 +506,7 @@ are inherited by all other classes:
 
 =item isa(CLASS)
 
-C<isa> returns I<true> if its object is blessed into a sub-class of C<CLASS>
+C<isa> returns I<true> if its object is blessed into a subclass of C<CLASS>
 
 C<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:
@@ -286,7 +547,7 @@ You do not need to C<use UNIVERSAL> in order to make these methods
 available to your program.  This is necessary only if you wish to
 have C<isa> available as a plain subroutine in the current package.
 
-=head2 TIEHANDLE Now Supported
+=head2 TIEHANDLE now supported
 
 See L<perltie> for other kinds of tie()s.
 
@@ -298,9 +559,9 @@ 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 "<shout>\n"; 
-	my $i; 
+    sub TIEHANDLE {
+	print "<shout>\n";
+	my $i;
 	return bless \$i, shift;
     }
 
@@ -310,38 +571,75 @@ 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; 
-	$$r++; 
+    sub PRINT {
+	$r = shift;
+	$$r++;
 	return print join( $, => map {uc} @_), $\;
     }
 
+=item PRINTF this, LIST
+
+This method will be triggered every time the tied handle is printed to
+with the C<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";
+    }
+
+=item READ this LIST
+
+This method will be called when the handle is read from via the C<read>
+or C<sysread> functions.
+
+    sub READ {
+	$r = shift;
+	my($buf,$len,$offset) = @_;
+	print "READ called, \$buf=$buf, \$len=$len, \$offset=$offset";
+    }
+
 =item 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 $$r times\n"; 
+    sub READLINE {
+	$r = shift;
+	return "PRINT called $$r times\n"
     }
 
+=item GETC this
+
+This method will be called when the C<getc> function is called.
+
+    sub GETC { print "Don't GETC, Get Perl"; return "a"; }
+
 =item 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 { 
+    sub DESTROY {
 	print "</shout>\n";
     }
 
 =back
 
-=head2 Malloc Enhancements
+=head2 Malloc enhancements
+
+Four new compilation flags are recognized by malloc.c.  (They have no
+effect if perl is compiled with system malloc().)
+
+=over
+
+=item -DDEBUGGING_MSTATS
 
-If perl's malloc() is used, you can print memory statistics at runtime
-by running Perl thusly:
+If perl is compiled with C<DEBUGGING_MSTATS> defined, you can print
+memory statistics at runtime by running Perl thusly:
 
   env PERL_DEBUG_MSTATS=2 perl your_script_here
 
@@ -350,11 +648,6 @@ exit; with a value of 1, the statistics ares printed only on exit.
 (If you want the statistics at an arbitrary time, you'll need to
 install the optional module Devel::Peek.)
 
-In addition, three new compilation flags are recognized by malloc.c.
-(They have no effect if perl is compiled with system malloc().)
-
-=over
-
 =item -DEMERGENCY_SBRK
 
 If this macro is defined, running out of memory need not be a fatal
@@ -395,21 +688,63 @@ negligible.
 
 =back
 
-=head2 Miscellaneous Efficiency Enhancements
+=head2 Miscellaneous efficiency enhancements
 
 Functions that have an empty prototype and that do nothing but return
 a fixed value are now inlined (e.g. C<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 re-allocated.
+same hash, the hash keys never have to be reallocated.
+
+=head1 Support for More Operating Systems
+
+Support for the following operating systems is new in Perl 5.004.
+
+=head2 Win32
+
+Perl 5.004 now includes support for building a "native" perl under
+Windows 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 L<MakeMaker> and L<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 L<README.win32> 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 L<README.cygwin32> for
+more details on this port, and how to obtain the Cygwin32 toolkit.
+
+=head2 Plan 9
+
+See L<README.plan9>.
+
+=head2 QNX
+
+See L<README.qnx>.
+
+=head2 AmigaOS
+
+See L<README.amigaos>.
 
 =head1 Pragmata
 
-Four new pragmatic modules exist:
+Six new pragmatic modules exist:
 
 =over
 
+=item use autouse MODULE => qw(sub1 sub2 sub3)
+
+Defers C<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.
+
 =item use blib
 
 =item use blib 'dir'
@@ -421,10 +756,15 @@ parent directories.
 Intended for use on command line with B<-M> option as a way of testing
 arbitrary scripts against an uninstalled version of a package.
 
+=item use constant NAME => VALUE
+
+Provides a convenient interface for creating compile-time constants,
+See L<perlsub/"Constant Functions">.
+
 =item use locale
 
 Tells the compiler to enable (or disable) the use of POSIX locales for
-built-in operations.
+builtin operations.
 
 When C<use locale> is in effect, the current LC_CTYPE locale is used
 for regular expressions and case mapping; LC_COLLATE for string
@@ -456,7 +796,22 @@ relative to the local time zone, in the VMS tradition.
 
 =head1 Modules
 
-=head2 Installation Directories
+=head2 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, 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.
+
+=head2 Installation directories
 
 The I<installperl> script now places the Perl source files for
 extensions in the architecture-specific library directory, which is
@@ -466,38 +821,21 @@ library directory unchanged from a previous version, without running
 the risk of binary incompatibility between extensions' Perl source and
 shared libraries.
 
-=head2 Fcntl
-
-New constants in the existing Fcntl modules are now supported,
-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 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 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. C<use Fcntl ':flock'>).
-
-=head2 Module Information Summary
+=head2 Module information summary
 
 Brand new modules, arranged by topic rather than strictly
 alphabetically:
 
-    CPAN                 interface to Comprehensive Perl Archive Network
-    CPAN::FirstTime      create a CPAN configuration file
-    CPAN::Nox            run CPAN while avoiding compiled extensions
+    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
@@ -514,22 +852,46 @@ alphabetically:
 
     FindBin.pm           Find path of currently executing program
 
-    Class/Template.pm    Structure/member template builder
-    File/stat.pm         Object-oriented wrapper around CORE::stat
-    Net/hostent.pm       Object-oriented wrapper around CORE::gethost*
-    Net/netent.pm        Object-oriented wrapper around CORE::getnet*
-    Net/protoent.pm      Object-oriented wrapper around CORE::getproto*
-    Net/servent.pm       Object-oriented wrapper around CORE::getserv*
-    Time/gmtime.pm       Object-oriented wrapper around CORE::gmtime
-    Time/localtime.pm    Object-oriented wrapper around CORE::localtime
-    Time/tm.pm           Perl implementation of "struct tm" for {gm,local}time
-    User/grent.pm        Object-oriented wrapper around CORE::getgr*
-    User/pwent.pm        Object-oriented wrapper around CORE::getpw*
+    Class/Struct.pm      Declare struct-like datatypes as Perl classes
+    File/stat.pm         By-name interface to Perl's builtin stat
+    Net/hostent.pm       By-name interface to Perl's builtin gethost*
+    Net/netent.pm        By-name interface to Perl's builtin getnet*
+    Net/protoent.pm      By-name interface to Perl's builtin getproto*
+    Net/servent.pm       By-name interface to Perl's builtin getserv*
+    Time/gmtime.pm       By-name interface to Perl's builtin gmtime
+    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
 
+=head2 Fcntl
+
+New constants in the existing Fcntl modules are now supported,
+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 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 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. C<use Fcntl ':flock'>).
+
 =head2 IO
 
 The IO module provides a simple mechanism to load all of the IO modules at one
@@ -554,11 +916,22 @@ more operations.  These are overloaded:
 And these functions are now exported:
 
     pi i Re Im arg
-    log10 logn cbrt root
-    tan cotan asin acos atan acotan
-    sinh cosh tanh cotanh asinh acosh atanh acotanh
+    log10 logn ln cbrt root
+    tan
+    csc sec cot
+    asin acos atan
+    acsc asec acot
+    sinh cosh tanh
+    csch sech coth
+    asinh acosh atanh
+    acsch asech acoth
     cplx cplxe
 
+=head2 Math::Trig
+
+This new module provides a simpler interface to parts of Math::Complex for
+those who need trigonometric functions only for real numbers.
+
 =head2 DB_File
 
 There have been quite a few changes made to DB_File. Here are a few of
@@ -605,9 +978,9 @@ 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.
 
-=head2 Overridden Built-ins
+=head2 Object-oriented overrides for builtin operators
 
-Many of the Perl built-ins returning lists now have
+Many of the Perl builtins returning lists now have
 object-oriented overrides.  These are:
 
     File::stat
@@ -628,6 +1001,19 @@ For example, you can now say
 
 =head1 Utility Changes
 
+=head2 pod2html
+
+=over
+
+=item Sends converted HTML to standard output
+
+The I<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 I<pod2html> did.
+Use the B<--outfile=FILENAME> option to write to a file.
+
+=back
+
 =head2 xsubpp
 
 =over
@@ -671,12 +1057,19 @@ C<perl_call_sv> is Perl's producing an "Undefined subroutine called"
 error on the I<second> call to a given method (since there is no cache
 on the first call).
 
+=item C<perl_eval_pv>
+
+A new function handy for eval'ing 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 table.  See
+L<perlguts>, L<perlembed> and L<perlcall> for details and examples.
+
 =item 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 C<SV*>s, so that C<tied> hashes can be given
-real scalars as keys rather than plain strings (non-tied hashes still
+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 C<SV*> keys.  These
 additions also make it feasible to manipulate C<HE*>s (hash entries),
@@ -695,6 +1088,10 @@ new pods are included in section 1:
 
 This document.
 
+=item L<perlfaq>
+
+Frequently asked questions.
+
 =item L<perllocale>
 
 Locale support (internationalization and localization).
@@ -707,6 +1104,11 @@ Tutorial on Perl OO programming.
 
 Perl internal IO abstraction interface.
 
+=item L<perlmodlib>
+
+Perl module library and recommended practice for module creation.
+Extracted from L<perlmod> (which is much smaller as a result).
+
 =item L<perldebug>
 
 Although not new, this has been massively updated.
@@ -721,7 +1123,7 @@ Although not new, this has been massively updated.
 
 Several new conditions will trigger warnings that were
 silent before.  Some only affect certain platforms.
-The following new warnings and errors outline these.  
+The following new warnings and errors outline these.
 These messages are classified as follows (listed in
 increasing order of desperation):
 
@@ -730,7 +1132,7 @@ increasing order of desperation):
    (S) A severe warning (mandatory).
    (F) A fatal error (trappable).
    (P) An internal error you should never see (trappable).
-   (X) A very fatal error (non-trappable).
+   (X) A very fatal error (nontrappable).
    (A) An alien error message (not generated by Perl).
 
 =over
@@ -757,13 +1159,22 @@ or a hash slice, such as
 
 =item Allocation too large: %lx
 
-(X) You can't allocate more than 64K on an MSDOS machine.
+(X) You can't allocate more than 64K on an MS-DOS machine.
 
 =item Allocation too large
 
 (F) You can't allocate more than 2^31+"small amount" bytes.
 
-=item Attempt to free non-existent shared string
+=item Applying %s to %s will act on scalar(%s)
+
+(W) The pattern match (//), substitution (s///), and translation (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
+L<perlfunc/grep> and L<perlfunc/map> for alternatives.
+
+=item 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
@@ -776,39 +1187,68 @@ that can no longer be found in the table.
 as an lvalue, which is pretty strange.  Perhaps you forgot to
 dereference it first.  See L<perlfunc/substr>.
 
-=item Unsupported function fork
+=item Can't redefine active sort subroutine %s
 
-(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 C<perl_>, C<perl__>, and so on.
-
-=item 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 non-standard names,
-or it may indicate that a logical name table has been corrupted.
+(F) Perl optimizes the internal handling of sort subroutines and keeps
+pointers into them.  You tried to redefine one such sort subroutine when it
+was currently active, which is not allowed.  If you really want to do
+this, you should write C<sort { &func } @x> instead of C<sort func @x>.
 
 =item 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 L<perlref>.
 
+=item 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).
+
 =item Constant subroutine %s redefined
 
 (S) You redefined a subroutine which had previously been eligible for
 inlining.  See L<perlsub/"Constant Functions"> for commentary and
 workarounds.
 
+=item Constant subroutine %s undefined
+
+(S) You undefined a subroutine which had previously been eligible for
+inlining.  See L<perlsub/"Constant Functions"> for commentary and
+workarounds.
+
+=item Copy method did not return a reference
+
+(F) The method which overloads "=" is buggy. See L<overload/Copy Constructor>.
+
 =item Died
 
 (F) You passed die() an empty string (the equivalent of C<die "">) or
 you called it with no args and both C<$@> and C<$_> were empty.
 
+=item 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 L<perlfunc/sort>.
+
+=item Identifier too long
+
+(F) Perl limits identifiers (names for variables, functions, etc.) to
+252 characters for simple names, somewhat more for compound names (like
+C<$A::B>).  You've exceeded Perl's limits.  Future versions of Perl are
+likely to eliminate these arbitrary limitations.
+
+=item 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., C<print E<lt>E<lt>EOF;>).
+
+=item Illegal switch in PERL5OPT: %s
+
+(X) The PERL5OPT environment variable may only be used to set the
+following switches: B<-[DIMUdmw]>.
+
 =item Integer overflow in hex number
 
 (S) The literal hex number you have specified is too big for your
@@ -821,6 +1261,30 @@ architecture. On a 32-bit architecture the largest hex literal is
 architecture. On a 32-bit architecture the largest octal literal is
 037777777777.
 
+=item internal error: glob failed
+
+(P) Something went wrong with the external program(s) used for C<glob>
+and C<E<lt>*.cE<gt>>.  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
+were csh (e.g. C<full_csh='/usr/bin/tcsh'>); otherwise, make them all
+empty (except that C<d_csh> should be C<'undef'>) so that Perl will
+think csh is missing.  In either case, after editing config.sh, run
+C<./Configure -S> and rebuild Perl.
+
+=item Invalid conversion in %s: "%s"
+
+(W) Perl does not understand the given format conversion.
+See L<perlfunc/sprintf>.
+
+=item Invalid type in pack: '%s'
+
+(F) The given character is not a valid pack type.  See L<perlfunc/pack>.
+
+=item Invalid type in unpack: '%s'
+
+(F) The given character is not a valid unpack type.  See L<perlfunc/unpack>.
+
 =item Name "%s::%s" used only once: possible typo
 
 (W) Typographical errors often show up as unique variable names.
@@ -841,17 +1305,6 @@ pointing outside the buffer.  This is difficult to imagine.
 The sole exception to this is that C<sysread()>ing past the buffer
 will extend the buffer and zero pad the new area.
 
-=item Stub found while resolving method `%s' overloading `%s' in package `%s'
-
-(P) Overloading resolution over @ISA tree may be broken by importing stubs.
-Stubs should never be implicitely created, but explicit calls to C<can>
-may break this.
-
-=item 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).
-
 =item Out of memory!
 
 (X|F) The malloc() function returned 0, indicating there was insufficient
@@ -870,6 +1323,10 @@ 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.
 
+=item panic: frexp
+
+(P) The library function frexp() failed, making printf("%f") impossible.
+
 =item Possible attempt to put comments in qw() list
 
 (W) qw() lists contain items separated by whitespace; as with literal
@@ -880,7 +1337,7 @@ used.)
 
 You probably wrote something like this:
 
-    @list = qw( 
+    @list = qw(
         a # a comment
         b # another comment
     );
@@ -888,7 +1345,7 @@ You probably wrote something like this:
 when you should have written this:
 
     @list = qw(
-        a 
+        a
         b
     );
 
@@ -907,7 +1364,7 @@ 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: 
+You probably wrote something like this:
 
     qw! a, b, c !;
 
@@ -925,18 +1382,58 @@ assigning to it and when evaluating its argument, while C<@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.
 
+=item Stub found while resolving method `%s' overloading `%s' in package `%s'
+
+(P) Overloading resolution over @ISA tree may be broken by importing stubs.
+Stubs should never be implicitely created, but explicit calls to C<can>
+may break this.
+
+=item Too late for "B<-T>" option
+
+(X) The #! line (or local equivalent) in a Perl script contains the
+B<-T> option, but Perl was not invoked with B<-T> in its argument
+list.  This is an error because, by the time Perl discovers a B<-T> in
+a script, it's too late to properly taint everything from the
+environment.  So Perl gives up.
+
 =item untie attempted while %d inner references still exist
 
 (W) A copy of the object returned from C<tie> (or C<tied>) was still
 valid when C<untie> was called.
 
-=item Value of %s construct can be "0"; test with defined()
+=item Unrecognized character %s
+
+(F) The Perl parser has no idea what to do with the specified character
+in your Perl script (or eval).  Perhaps you tried to run a compressed
+script, a binary program, or a directory as a Perl program.
 
-(W) In a conditional expression, you used <HANDLE>, <*> (glob), or
-C<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 C<defined> operator.
+=item 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 C<perl_>, C<perl__>, and so on.
+
+=item 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.
+
+=item Value of %s can be "0"; test with defined()
+
+(W) In a conditional expression, you used <HANDLE>, <*> (glob), C<each()>,
+or C<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 C<defined> operator.
 
 =item Variable "%s" may be unavailable
 
@@ -979,7 +1476,7 @@ will I<never> share the given variable.
 This problem can usually be solved by making the inner subroutine
 anonymous, using the C<sub {}> syntax.  When inner anonymous subs that
 reference variables in outer subroutines are called or referenced,
-they are automatically re-bound to the current values of such
+they are automatically rebound to the current values of such
 variables.
 
 =item Warning: something's wrong
@@ -987,6 +1484,15 @@ variables.
 (W) You passed warn() an empty string (the equivalent of C<warn "">) or
 you called it with no args and C<$_> was empty.
 
+=item 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.
+
 =item Got an error from DosAllocMem
 
 (P) An error peculiar to OS/2.  Most probably you're using an obsolete
@@ -994,7 +1500,7 @@ version of Perl, and this should not happen anyway.
 
 =item Malformed PERLLIB_PREFIX
 
-(F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form
+(F) An error peculiar to OS/2.  PERLLIB_PREFIX should be of the form
 
     prefix1;prefix2
 
@@ -1002,21 +1508,23 @@ or
 
     prefix1 prefix2
 
-with non-empty prefix1 and prefix2. If C<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 L<perlos2/"PERLLIB_PREFIX">.
+with nonempty prefix1 and prefix2.  If C<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
+"PERLLIB_PREFIX" in F<README.os2>.
 
 =item PERL_SH_DIR too long
 
 (F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the
-C<sh>-shell in. See L<perlos2/"PERL_SH_DIR">.
+C<sh>-shell in.  See "PERL_SH_DIR" in F<README.os2>.
 
 =item 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 sighandlers, see
-L<perlipc/"Signals">.  See L<perlos2/"Process terminated by SIGTERM/SIGINT">.
+applications die in silence.  It is considered a feature of the OS/2
+port.  One can easily disable this by appropriate sighandlers, see
+L<perlipc/"Signals">.  See also "Process terminated by SIGTERM/SIGINT"
+in F<README.os2>.
 
 =back
 
@@ -1028,10 +1536,10 @@ There may also be information at http://www.perl.com/perl/, the Perl
 Home Page.
 
 If you believe you have an unreported bug, please run the B<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 C<perl -V>, will be sent off to F<perlbug@perl.com>
-to be analysed by the Perl porting team.
+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 C<perl -V>, will be sent off to <F<perlbug@perl.com>> to be
+analysed by the Perl porting team.
 
 =head1 SEE ALSO
 
@@ -1051,4 +1559,4 @@ Constructed by Tom Christiansen, grabbing material with permission
 from innumerable contributors, with kibitzing by more than a few Perl
 porters.
 
-Last update: Tue Jan 14 14:03:02 EST 1997
+Last update: Wed May 14 11:14:09 EDT 1997