=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 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
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
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->bar()> or C<$obj->bar()>).
+(e.g. C<Foo-E<gt>bar()> or C<$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
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
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, 5.001, and 5.002 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.
+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:
not. In Perl 5.002 and 5.003, both $a{b} and $a[2] would have existed
(but $a[2]'s value would have been undefined).
-=head2 C<$)> is writable
+=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, due to an oversight, assigning to C<$)> has not called
-C<setgroups()>, only C<setegid()>.
+reflected not only the current effective group, but also the group list
+as returned by the C<getgroups()> C function (if there is one).
+However, until this release, there has not been a way to call the
+C<setgroups()> C function from Perl.
-In Perl 5.004, assigning to C<$)> is exactly symmetrical with
-examining it: The first number in its string value is used as the
-effective gid, and all the others are passed to the C<setgroups()> C
-function (if there is one).
+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.
old (broken) way inside strings; but it generates this message as a
warning. And in Perl 5.005, this special treatment will cease.
+=head2 Fixed localization of $<digit>, $&, etc.
+
+Perl versions before 5.004 did not always properly localize the
+regex-related special variables. Perl 5.004 does localize them, as
+the documentation has always said it should. This may result in $1,
+$2, etc. no longer being set where existing programs use them.
+
=head2 No resetting of $. on implicit close
The documentation for Perl 5.0 has always stated that C<$.> is I<not>
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 C<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 determination.
+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".
+
=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
+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
+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
IO::Handle, 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, C<*GLOB{FILEHANDLE}> is now a
-backward-compatible synonym for C<*STDOUT{IO}>.
+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
instead of stdio. See L<perlapio> for more details, and
the F<INSTALL> file for how to use it.
+=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
By default, running out of memory it is not trappable. However, if
compiled for this, Perl may use the contents of C<$^M> as an emergency
pool after die()ing with this message. Suppose that your Perl were
-compiled with -DEMERGENCY_SBRK and used Perl's malloc. Then
+compiled with -DPERL_EMERGENCY_SBRK and used Perl's malloc. Then
$^M = 'a' x (1<<16);
=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
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
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
+pointer.
+
+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
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 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>.
+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>.
=item C<m//x> ignores whitespace before ?*+{}
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
.
+
+However, it still fails (without a warning) if the foreach is within a
+subroutine:
+
+ my $i;
+ sub foo {
+ foreach $i ( 1 .. 10 ) {
write;
+ }
}
+ foo;
+ format =
+ my i is @#
+ $i
+ .
=back
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>
=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 is compiled with C<DEBUGGING_MSTATS> defined, you can print
+If perl is compiled with the malloc included with the perl distribution
+(that is, if C<perl -V:d_mymalloc> is 'define') then you can print
memory statistics at runtime by running Perl thusly:
env PERL_DEBUG_MSTATS=2 perl your_script_here
The value of 2 means to print statistics after compilation and on
-exit; with a value of 1, the statistics ares printed only on exit.
+exit; with a value of 1, the statistics are printed only on exit.
(If you want the statistics at an arbitrary time, you'll need to
install the optional module Devel::Peek.)
-=item -DEMERGENCY_SBRK
+Three new compilation flags are recognized by malloc.c. (They have no
+effect if perl is compiled with system malloc().)
+
+=over
+
+=item -DPERL_EMERGENCY_SBRK
If this macro is defined, running out of memory need not be a fatal
error: a memory pool can allocated by assigning to the special
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.
+=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
Six new pragmatic modules exist:
Module Required Version for Perl 5.004
------ -------------------------------
- Filter 1.12
- LWP 5.08
+ 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
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
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
=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
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
This document.
+=item L<perlfaq>
+
+Frequently asked questions.
+
=item L<perllocale>
Locale support (internationalization and localization).
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.
=item "my" variable %s masks earlier declaration in same scope
-(S) A lexical variable has been redeclared in the same scope, effectively
+(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
=item Applying %s to %s will act on scalar(%s)
-(W) The pattern match (//), substitution (s///), and translation (tr///)
+(W) The pattern match (//), substitution (s///), and transliteration (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
as an lvalue, which is pretty strange. Perhaps you forgot to
dereference it first. See L<perlfunc/substr>.
+=item Bareword "%s" refers to nonexistent package
+
+(W) You used a qualified bareword of the form C<Foo::>, but
+the compiler saw no other uses of that namespace before that point.
+Perhaps you need to predeclare a package?
+
+=item Can't 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 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
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
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.
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
qw! a b c !;
-=item Recursive substitution detected
-
-(F) The replacement string of a substitution caused the recursive
-execution of that very same substituion. Perl cannot keep track of
-special variables (C<$1>, etc.) under such circumstances.
-
=item Scalar value @%s{%s} better written as $%s{%s}
(W) You've used a hash slice (indicated by @) to select a single element of
from innumerable contributors, with kibitzing by more than a few Perl
porters.
-Last update: Sat Mar 8 19:51:26 EST 1997
+Last update: Wed May 14 11:14:09 EDT 1997