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perl5004delta ()
  • >> perl5004delta (1) ( Solaris man: Команды и прикладные программы пользовательского уровня )
  • perl5004delta (1) ( Разные man: Команды и прикладные программы пользовательского уровня )
  • 
    
    

    NAME

         perldelta - what's new for perl5.004
    
    
    

    DESCRIPTION

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

    Supported Environments

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

    Core Changes

         Most importantly, many bugs were fixed, including several
         security problems.  See the Changes file in the 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).
    
         "Can't locate Foo.pm in @INC" error now lists @INC
    
         Compilation option: Binary compatibility with 5.003
    
         There is a new Configure question that asks if you want to
         maintain binary compatibility with Perl 5.003.  If you
         choose binary compatibility, you do not have to recompile
         your extensions, but you might have symbol conflicts if you
         embed Perl in another application, just as in the 5.003
         release.  By default, binary compatibility is 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 variable as if its contents had appeared on a
         "#!perl" line at the beginning of your script, except that
         hyphens are optional.  PERL5OPT may only be used to set the
         following switches: -[DIMUdmw].
    
         Limitations on -M, -m, and -T options
    
         The `-M' and `-m' options are no longer allowed on the `#!'
         line of a script.  If a script needs a module, it should
         invoke it with the `use' pragma.
    
    
         The -T option is also forbidden on the `#!' line of a
         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', while:
    
             #!/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.  However, there is a significant base of
         existing code that may be using the old behavior.  So, as an
         interim step, Perl 5.004 issues an optional warning when a
         non-method uses an inherited `AUTOLOAD'.
    
         The simple rule is:  Inheritance will not work when
         autoloading non-methods.  The simple fix for old code is:
         In any module that used to depend on inheriting `AUTOLOAD'
         for non-methods from a base class named `BaseClass', execute
         `*AUTOLOAD = \&BaseClass::AUTOLOAD' during startup.
    
         Previously deprecated %OVERLOAD is no longer usable
    
         Using %OVERLOAD to define overloading was deprecated in
         5.003.  Overloading is now defined using the overload
         pragma. %OVERLOAD is still used internally but should not be
         used by Perl scripts. See the overload manpage for more
         details.
    
         Subroutine arguments created only when they're modified
    
         In Perl 5.004, nonexistent array and hash elements used as
         subroutine parameters are brought into existence only if
         they are actually assigned to (via `@_').
    
         Earlier versions of Perl vary in their handling of such
         arguments.  Perl versions 5.002 and 5.003 always brought
         them into existence.  Perl versions 5.000 and 5.001 brought
         them into existence only if they were not the first argument
         (which was almost certainly a bug).  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).
    
         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 `setgroups()' 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 $$<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.
    
         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.
    
         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
         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.
    
         `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".
    
    
         Changes to tainting checks
    
         A bug in previous versions may have failed to detect some
         insecure conditions when taint checks are turned on.  (Taint
         checks are used in setuid or setgid scripts, or when
         explicitly turned on with the `-T' invocation option.)
         Although it's unlikely, this may cause a 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 program.
    
         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.
    
         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).
    
         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.
    
         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 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.
    
         In harmony with this change, `*GLOB{FILEHANDLE}' is now just
         a backward-compatible synonym for `*GLOB{IO}'.
    
         Internal change: PerlIO abstraction interface
    
         It is now possible to build Perl with AT&T's sfio IO package
         instead of stdio.  See the perlapio manpage for more
         details, and the INSTALL file for how to use it.
    
         New and changed syntax
    
         $coderef->(PARAMS)
             A subroutine reference may now be suffixed with an arrow
             and a (possibly empty) parameter list.  This syntax
             denotes a call of the referenced subroutine, with the
             given parameters (if any).
    
             This new syntax follows the pattern of `$hashref->{FOO}'
             and `$aryref->[$foo]': You may now write
             `&$subref($foo)' as `$subref->($foo)'.  All these arrow
             terms may be chained; thus, `&{$table->{FOO}}($bar)' may
             now be written `$table->{FOO}->($bar)'.
    
         New and changed builtin constants
    
         __PACKAGE__
             The current package name at compile time, or the
             undefined value if there is no current package (due to a
             `package;' directive).  Like `__FILE__' and `__LINE__',
             `__PACKAGE__' does not interpolate into strings.
    
         New and changed builtin variables
    
         $^E Extended error message on some platforms.  (Also known
             as $EXTENDED_OS_ERROR if you `use English').
    
         $^H The current set of syntax checks enabled by `use
             strict'.  See the documentation of `strict' for more
             details.  Not actually new, but newly documented.
             Because it is intended for internal use by Perl core
             components, there is no `use English' long name for this
             variable.
    
         $^M By default, running out of memory it is not trappable.
             However, if compiled for this, Perl may use the contents
             of `$^M' as an emergency pool after die()ing with this
             message.  Suppose that your Perl were compiled with
             -DPERL_EMERGENCY_SBRK and used Perl's 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'}')
    
         flock
             is now supported on more platforms, prefers fcntl to
             lockf when emulating, and always flushes before
             (un)locking.
    
         printf and sprintf
             Perl now implements these functions itself; it doesn't
             use the C library function sprintf() any more, except
             for floating-point numbers, and even then only known
             flags are allowed.  As a result, it is now possible to
             know which conversions and flags will work, and what
             they will do.
    
             The new conversions in Perl's sprintf() are:
    
                %i   a synonym for %d
                %p   a pointer (the address of the Perl value, in hexadecimal)
                %n   special: *stores* the number of characters output so far
                     into the next variable in the parameter list
    
             The new flags that go between the `%' and the 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 the sprintf entry in the perlfunc manpage for a
             complete list of conversion and flags.
    
         keys as an lvalue
             As an lvalue, `keys' allows you to increase the number
             of hash buckets allocated for the given hash.  This can
             gain you a measure of efficiency if you know the hash is
             going to get big.  (This is similar to pre-extending an
             array by assigning a larger number to $#array.)  If you
             say
    
                 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 can't
             shrink the number of buckets allocated for the hash
             using `keys' in this way (but you needn't 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 control expressions of control structures such
             as:
    
                 while (defined(my $line = <>)) {
                     $line = lc $line;
                 } continue {
                     print $line;
                 }
    
                 if ((my $answer = <STDIN>) =~ /^y(es)?$/i) {
                     user_agrees();
                 } elsif ($answer =~ /^n(o)?$/i) {
                     user_disagrees();
                 } else {
                     chomp $answer;
                     die "`$answer' is neither `yes' nor `no'";
                 }
    
             Also, you can declare a foreach loop control variable as
             lexical by preceding it with the word "my".  For
             example, in:
    
                 foreach my $i (1, 2, 3) {
                     some_function();
                 }
    
             $i is a lexical variable, and the scope of $i extends to
             the end of the loop, but not beyond it.
    
             Note that you still cannot use my() on global
             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 significant first.  Bit eight
             of each byte is set, except for the last byte, in which
             bit eight is clear.
    
             If 'p' or 'P' are given undef as values, they now
             generate a NULL pointer.
    
             Both pack() and unpack() now fail when their templates
             contain invalid types.  (Invalid types used to be
             ignored.)
    
         sysseek()
             The new sysseek() operator is a variant of seek() that
             sets and gets the file's system read/write position,
             using the lseek(2) system call.  It is the only reliable
             way to seek before using sysread() 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 version 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, inherited 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 don't use the
             Exporter.  It is the recommended method for new code.
    
         prototype(FUNCTION)
             Returns the prototype of a function as a string (or
             `undef' if the function has no prototype).  FUNCTION is
             a reference to or the name of the function whose
             prototype you want to retrieve.  (Not actually new; just
             never documented before.)
    
         srand
             The default seed for `srand', which used to be `time',
             has been changed.  Now it's a heady mix of difficult-
             to-predict system-dependent values, which should be
             sufficient for most everyday purposes.
    
             Previous to version 5.004, calling `rand' without first
             calling `srand' would yield the same sequence of random
             numbers on most or all machines.  Now, when perl sees
             that you're calling `rand' and haven't yet called
             `srand', it calls `srand' with the default seed. You
             should still call `srand' manually if your code might
             ever be run on a pre-5.004 system, of course, or if you
             want a seed other than the default.
    
         $_ as Default
             Functions documented in the Camel to default to $_ now
             in fact do, and all those that do are so documented in
             the perlfunc manpage.
    
         `m//gc' does not reset search position on failure
             The `m//g' match iteration construct has always reset
             its target string's search position (which is visible
             through the `pos' operator) when a match fails; as a
             result, the next `m//g' match after a failure starts
             again at the beginning of the string.  With Perl 5.004,
             this reset may be disabled by adding the "c" (for
             "continue") modifier, i.e. `m//gc'.  This feature, in
             conjunction with the `\G' zero-width assertion, makes it
             possible to chain matches together.  See the perlop
             manpage and the perlre manpage.
    
         `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 example, `/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
             didn't 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), formats now work properly.  For
             example, this silently failed before (printed only
             zeros), but is fine now:
    
                 my $i;
                 foreach $i ( 1 .. 10 ) {
                     write;
                 }
                 format =
                     my i is @#
                     $i
                 .
    
             However, it still fails (without a warning) if the
             foreach is within a subroutine:
    
                 my $i;
                 sub foo {
                   foreach $i ( 1 .. 10 ) {
                     write;
                   }
                 }
                 foo;
                 format =
                     my i is @#
                     $i
                 .
    
    
         New builtin methods
    
         The `UNIVERSAL' package automatically contains the following
         methods that are inherited by all other classes:
    
         isa(CLASS)
             `isa' returns true if its object is blessed into a
             subclass of `CLASS'
    
             `isa' is also exportable and can be called as a sub with
             two arguments. This allows the ability to check what a
             reference points to. Example:
    
                 use UNIVERSAL qw(isa);
    
                 if(isa($ref, 'ARRAY')) {
                    ...
                 }
    
    
         can(METHOD)
             `can' checks to see if its object has a method called
             `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 version (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 automatically by the `VERSION' form of `use'.
    
                 use A 1.2 qw(some imported subs);
                 # implies:
                 A->VERSION(1.2);
    
    
         NOTE: `can' directly uses Perl's internal code for method
         lookup, and `isa' uses a very similar method and caching
         strategy. This may cause strange effects if the Perl code
         dynamically changes @ISA in any package.
    
         You may add other methods to the UNIVERSAL class via Perl or
         XS code.  You do not need to `use UNIVERSAL' in order to
         make these methods available to your program.  This is
         necessary only if you wish to have `isa' available as a
         plain subroutine in the current package.
    
         TIEHANDLE now supported
    
         See the perltie manpage 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 "<shout>\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;
                     $$r++;
                     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 {
                     shift;
                       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 "Don't GETC, Get Perl"; return "a"; }
    
    
         DESTROY this
             As with the other types of ties, this method will be
             called when the tied handle is about to be destroyed.
             This is useful for debugging and possibly for cleaning
             up.
    
                 sub DESTROY {
                     print "</shout>\n";
                 }
    
    
         Malloc enhancements
    
         If perl is compiled with the malloc included with the perl
         distribution (that is, if `perl -V:d_mymalloc' is 'define')
         then you can print memory statistics at runtime by running
         Perl thusly:
    
           env PERL_DEBUG_MSTATS=2 perl your_script_here
    
         The value of 2 means to print statistics after compilation
         and on exit; with a value of 1, the statistics are printed
         only on exit.  (If you want the statistics at an arbitrary
         time, you'll need to install the optional module
         Devel::Peek.)
    
         Three new compilation flags are recognized by malloc.c.
         (They have no effect if perl is compiled with system
         malloc().)
    
         -DPERL_EMERGENCY_SBRK
             If this macro is defined, running out of memory need not
             be a fatal error: a memory pool can allocated by
             assigning to the special variable `$^M'.  See the
             section on "$^M".
    
         -DPACK_MALLOC
             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 often).
    
             Expected memory savings (with 8-byte alignment in
             `alignbytes') is about 20% for typical Perl usage.
             Expected slowdown due to additional malloc overhead is
             in fractions of a percent (hard to measure, because of
             the effect of saved memory on speed).
    
         -DTWO_POT_OPTIMIZE
             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 negligible.
    
         Miscellaneous efficiency enhancements
    
         Functions that have an empty prototype and that do nothing
         but return a fixed value are now inlined (e.g. `sub PI () {
         3.14159 }').
    
         Each unique hash key is only allocated once, no matter how
         many hashes have an entry with that key.  So even if you
         have 100 copies of the same hash, the hash keys never have
         to be reallocated.
    
    
    

    Support for More Operating Systems

         Support for the following operating systems is new in Perl
         5.004.
    
         Win32
    
         Perl 5.004 now includes support for building a "native" perl
         under Windows NT, using the Microsoft Visual C++ 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 the
         MakeMaker manpage and the h2xs manpage, 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.
    
         QNX
    
         See README.qnx in the perl distribution.
    
         AmigaOS
    
         See README.amigaos in the perl distribution.
    
    
    

    Pragmata

         Six new pragmatic modules exist:
    
         use autouse MODULE => qw(sub1 sub2 sub3)
             Defers `require MODULE' until someone calls one of the
             specified subroutines (which must be exported by
             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 directories.
    
             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 constants, See the Constant Functions entry in the
             perlsub manpage.
    
         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 formating 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:\fIs0:setlocale().
    
             See the perllocale manpage for more information.
    
         use ops
             Disable unsafe opcodes, or any named opcodes, when
             compiling Perl code.
    
         use vmsish
             Enable VMS-specific language features.  Currently, there
             are three VMS-specific features available: 'status',
             which makes `$?' and `system' 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.
    
    
    

    Modules

         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.
    
         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 directory
         unchanged from a previous version, without running the risk
         of binary incompatibility between extensions' Perl source
         and shared libraries.
    
    
    
         Module information summary
    
         Brand new modules, arranged by topic rather than strictly
         alphabetically:
    
             CGI.pm               Web server interface ("Common Gateway Interface")
             CGI/Apache.pm        Support for Apache's Perl module
             CGI/Carp.pm          Log server errors with helpful context
             CGI/Fast.pm          Support for FastCGI (persistent server process)
             CGI/Push.pm          Support for server push
             CGI/Switch.pm        Simple interface for multiple server types
    
             CPAN                 Interface to Comprehensive Perl Archive Network
             CPAN::FirstTime      Utility for creating CPAN configuration file
             CPAN::Nox            Runs CPAN while avoiding compiled extensions
    
             IO.pm                Top-level interface to IO::* classes
             IO/File.pm           IO::File extension Perl module
             IO/Handle.pm         IO::Handle extension Perl module
             IO/Pipe.pm           IO::Pipe extension Perl module
             IO/Seekable.pm       IO::Seekable extension Perl module
             IO/Select.pm         IO::Select extension Perl module
             IO/Socket.pm         IO::Socket extension Perl module
    
             Opcode.pm            Disable named opcodes when compiling Perl code
    
             ExtUtils/Embed.pm    Utilities for embedding Perl in C programs
             ExtUtils/testlib.pm  Fixes up @INC to use just-built extension
    
             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 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
    
    
         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. `use Fcntl ':flock'').
    
         IO
    
         The IO module provides a simple mechanism to load all the IO
         modules at one go.  Currently this includes:
    
              IO::Handle
              IO::Seekable
              IO::File
              IO::Pipe
              IO::Socket
    
         For more information on any of these modules, please see its
         respective documentation.
    
         Math::Complex
    
         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
             tan
             csc sec cot
             asin acos atan
             acsc asec acot
             sinh cosh tanh
             csch sech coth
             asinh acosh atanh
             acsch asech acoth
             cplx cplxe
    
    
         Math::Trig
    
         This new module provides a simpler interface to parts of
         Math::Complex for those who need trigonometric functions
         only for real numbers.
    
         DB_File
    
         There have been quite a few changes made to DB_File. Here
         are a few of the highlights:
    
         o   Fixed a handful of bugs.
    
         o   By public demand, added support for the standard hash
             function exists().
    
         o   Made it compatible with Berkeley DB 1.86.
    
         o   Made negative subscripts work with RECNO interface.
    
         o   Changed the default flags from O_RDWR to O_CREAT|O_RDWR
             and the default mode from 0640 to 0666.
    
         o   Made DB_File automatically import the open() constants
             (O_RDWR, O_CREAT etc.) from Fcntl, if available.
    
         o   Updated documentation.
    
         Refer to the HISTORY section in DB_File.pm for a complete
         list of changes. Everything after DB_File 1.01 has been
         added since 5.003.
    
         Net::Ping
    
         Major rewrite - support added for both udp echo and real
         icmp pings.
    
    
    
         Object-oriented overrides for builtin operators
    
         Many of the Perl builtins returning lists now have object-
         oriented overrides.  These are:
    
             File::stat
             Net::hostent
             Net::netent
             Net::protoent
             Net::servent
             Time::gmtime
             Time::localtime
             User::grent
             User::pwent
    
         For example, you can now say
    
             use File::stat;
             use User::pwent;
             $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid);
    
    
    
    

    Utility Changes

         pod2html
    
         Sends converted HTML to standard output
             The pod2html utility included with Perl 5.004 is
             entirely new.  By default, it sends the converted HTML
             to its standard output, instead of writing it to a file
             like Perl 5.003's pod2html did.  Use the --
             outfile=FILENAME option to write to a file.
    
         xsubpp
    
         `void' XSUBs now default to returning nothing
             Due to a documentation/implementation bug in previous
             versions of Perl, XSUBs with a return type of `void'
             have actually been returning one value.  Usually that
             value was the GV for the XSUB, but sometimes it was some
             already freed or reused value, which would sometimes
             lead to program failure.
    
             In Perl 5.004, if an XSUB is declared as returning
             `void', it actually returns no value, i.e. an empty list
             (though there is a backward-compatibility 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 XSUB's return type is
             really `SV *'.
    
    
    

    C Language API Changes

         `gv_fetchmethod' and `perl_call_sv'
             The `gv_fetchmethod' function finds a method for an
             object, just like in Perl 5.003.  The GV it returns may
             be a method cache entry.  However, in Perl 5.004, method
             cache entries are not visible to users; 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 Perl's producing
             an "Undefined subroutine called" error on the second
             call to a given method (since there is no cache on the
             first call).
    
         `perl_eval_pv'
             A new function handy for eval'ing strings of Perl code
             inside C code.  This function returns the value from the
             eval statement, which can be used instead of fetching
             globals from the symbol table.  See the perlguts
             manpage, the perlembed manpage and the perlcall manpage
             for details and examples.
    
         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 the perlguts
             manpage for details.
    
    
    

    Documentation Changes

         Many of the base and library pods were updated.  These new
         pods are included in section 1:
    
         the perldelta manpage
             This document.
    
         the perlfaq manpage
             Frequently asked questions.
    
         the perllocale manpage
             Locale support (internationalization and localization).
    
         the perltoot manpage
             Tutorial on Perl OO programming.
    
         the perlapio manpage
             Perl internal IO abstraction interface.
    
         the perlmodlib manpage
             Perl module library and recommended practice for module
             creation.  Extracted from the perlmod manpage (which is
             much smaller as a result).
    
         the perldebug manpage
             Although not new, this has been massively updated.
    
         the perlsec manpage
             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
    
                 $foo{$bar}
                 $ref->[12]->{"susie"}
    
             or a hash slice, such as
    
                 @foo{$bar, $baz, $xyzzy}
                 @{$ref->[12]}{"susie", "queue"}
    
         Allocation too large: %lx
             (X) You can't allocate more than 64K on an MS-DOS
             machine.
    
         Allocation too large
             (F) You can't allocate more than 2^31+"small amount"
             bytes.
    
         Applying %s to %s will act on scalar(%s)
             (W) The pattern match (//), substitution (s///), and
             transliteration (tr///) operators work on scalar 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 the grep entry in the
             perlfunc manpage and the map entry in the perlfunc
             manpage 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 the
             substr entry in the perlfunc manpage.
    
         Bareword "%s" refers to nonexistent package
             (W) You used a qualified bareword of the form `Foo::',
             but the compiler saw no other uses of that namespace
             before that point.  Perhaps you need to predeclare a
             package?
    
         Can't redefine active sort subroutine %s
             (F) Perl optimizes the internal handling of sort
             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 `sort { &func } @x' instead of
             `sort func @x'.
    
         Can't use bareword ("%s") as %s ref while "strict refs" in use
             (F) Only hard references are allowed by "strict refs".
             Symbolic references are disallowed.  See the perlref
             manpage.
    
    
         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 the Constant Functions entry
             in the perlsub manpage for commentary and workarounds.
    
         Constant subroutine %s undefined
             (S) You undefined a subroutine which had previously been
             eligible for inlining.  See the Constant Functions entry
             in the perlsub manpage for commentary and workarounds.
    
         Copy method did not return a reference
             (F) The method which overloads "=" is buggy. See the
             Copy Constructor entry in the overload manpage.
    
         Died
             (F) You passed die() an empty string (the equivalent of
             `die ""') or you called it with no args and both `$@'
             and `$_' were empty.
    
         Exiting pseudo-block via %s
             (W) You are exiting a rather special block construct
             (like a sort block or subroutine) by unconventional
             means, such as a goto, or a loop control statement.  See
             the sort entry in the perlfunc manpage.
    
         Identifier too long
             (F) Perl limits identifiers (names for variables,
             functions, etc.) to 252 characters for simple names,
             somewhat more for compound names (like `$A::B').  You've
             exceeded Perl's limits.  Future versions of Perl are
             likely to eliminate these arbitrary limitations.
    
         Illegal character %s (carriage return)
             (F) A carriage return character was found in the input.
             This is an error, and not a warning, because carriage
             return characters can break multi-line strings,
             including here documents (e.g., `print <<EOF;').
    
         Illegal switch in PERL5OPT: %s
             (X) The PERL5OPT environment variable may only be used
             to set the following switches: -[DIMUdmw].
    
         Integer overflow in hex number
             (S) The literal hex number you have specified is too big
             for your architecture. On a 32-bit architecture the
             largest hex literal is 0xFFFFFFFF.
    
         Integer overflow in octal number
             (S) The literal octal number you have specified is too
             big for your architecture. On a 32-bit architecture the
             largest octal literal is 037777777777.
    
         internal error: glob failed
             (P) Something went wrong with the external program(s)
             used for `glob' and `<*.c>'.  This may mean that your
             csh (C shell) is broken.  If so, you should change all
             of the csh-related variables in config.sh:  If you have
             tcsh, make the variables refer to it as if it 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 the sprintf entry in the perlfunc
             manpage.
    
         Invalid type in pack: '%s'
             (F) The given character is not a valid pack type.  See
             the pack entry in the perlfunc manpage.
    
         Invalid type in unpack: '%s'
             (F) The given character is not a valid unpack type.  See
             the unpack entry in the perlfunc manpage.
    
         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 mention 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 the perlform manpage.
    
         Offset outside string
             (F) You tried to do a read/write/send/recv operation
             with an offset pointing outside the buffer.  This is
             difficult to imagine.  The sole exception to this is
             that `sysread()'ing past the buffer will extend the
             buffer and zero pad the new area.
    
         Out of memory!
             (X|F) The malloc() function returned 0, indicating there
             was insufficient remaining memory (or virtual memory) to
             satisfy the request.
    
             The request was judged to be small, so the possibility
             to trap it depends on the way Perl was compiled.  By
             default it is not trappable.  However, if compiled for
             this, Perl may use the contents of `$^M' as an emergency
             pool after die()ing with this message.  In this case the
             error is trappable once.
    
         Out of memory during request for %s
             (F) The malloc() function returned 0, indicating there
             was insufficient remaining memory (or virtual memory) to
             satisfy the request. However, the request was judged
             large enough (compile-time default is 64K), so a
             possibility to shut down by trapping this error is
             granted.
    
         panic: frexp
             (P) The library function frexp() failed, making
             printf("%f") impossible.
    
         Possible attempt to put comments in qw() list
             (W) qw() lists contain items separated by whitespace; as
             with literal strings, comment characters are not
             ignored, but are instead treated as literal data.  (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(
                     a
                     b
                 );
    
             If you really want comments, build your list the old-
             fashioned way, with quotes and commas:
    
                 @list = (
                     'a',    # a comment
                     'b',    # another comment
                 );
    
    
         Possible attempt to separate words with commas
             (W) qw() lists contain items separated by whitespace;
             therefore commas aren't needed to separate the items.
             (You may have used different delimiters than the
             parentheses shown here; braces are also frequently
             used.)
    
             You probably wrote something like this:
    
                 qw! a, b, c !;
    
             which puts literal commas into some of the list items.
             Write it without commas if you don't want them to appear
             in your data:
    
                 qw! a b c !;
    
    
         Scalar value @%s{%s} better written as $%s{%s}
             (W) You've used a hash slice (indicated by @) to select
             a single element of a hash.  Generally it's better to
             ask for a scalar value (indicated by $).  The difference
             is that `$foo{&bar}' always behaves like a scalar, both
             when assigning to it and when 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 you're expecting only one
             subscript.
    
    package `%s'
         Stub found while resolving method `%s' overloading `%s' in
             (P) Overloading resolution over @ISA tree may be broken
             by importing 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, it's too late to
             properly taint everything from the environment.  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 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.
    
         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 "$$<digit>" to mean "${$}<digit>" is deprecated
             (D) Perl versions before 5.004 misinterpreted any type
             marker followed by "$" and a digit.  For example, "$$0"
             was incorrectly taken to mean "${$}0" instead of
             "${$0}".  This bug is (mostly) fixed in Perl 5.004.
    
             However, the developers of Perl 5.004 could not fix this
             bug completely, because at least two widely-used modules
             depend on the old meaning of "$$0" in a string.  So Perl
             5.004 still interprets "$$<digit>" in the old (broken)
             way inside strings; but it generates this message as a
             warning.  And in Perl 5.005, this special treatment will
             cease.
    
         Value of %s can be "0"; test with defined()
             (W) In a conditional expression, you used <HANDLE>, <*>
             (glob), `each()', or `readdir()' as a boolean value.
             Each of these constructs can return a value of "0"; that
             would make the conditional expression false, which is
             probably not what you intended.  When using these
             constructs in conditional expressions, test their values
             with the `defined' operator.
    
         Variable "%s" may be unavailable
             (W) An inner (nested) anonymous subroutine is inside a
             named subroutine, and outside that is another
             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 variable 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
             probably not what you want.
    
             In these circumstances, it is usually best to make the
             middle subroutine 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 subroutine's 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
             subroutines 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 subroutines will never share the given
             variable.
    
             This problem can usually be solved by making the inner
             subroutine anonymous, using the `sub {}' syntax.  When
             inner anonymous subs that reference variables in outer
             subroutines are called or referenced, they are
             automatically rebound to the current values of such
             variables.
    
         Warning: something's wrong
             (W) You passed warn() an empty string (the equivalent of
             `warn ""') or you called it with no args and `$_' was
             empty.
    
         Ill-formed logical name |%s| in prime_env_iter
             (W) A warning peculiar to VMS.  A logical name was
             encountered when preparing to iterate over %ENV which
             violates the syntactic rules governing logical names.
             Since it cannot be translated normally, it is skipped,
             and will not appear in %ENV.  This may be a benign
             occurrence, as some software packages might directly
             modify logical name tables and introduce nonstandard
             names, or it may indicate that a logical name table has
             been corrupted.
    
         Got an error from DosAllocMem
             (P) An error peculiar to OS/2.  Most probably you're
             using an obsolete version of Perl, and this should not
             happen anyway.
    
         Malformed PERLLIB_PREFIX
             (F) An error peculiar to OS/2.  PERLLIB_PREFIX should be
             of the form
                 prefix1;prefix2
    
             or
    
                 prefix1 prefix2
    
             with nonempty prefix1 and prefix2.  If `prefix1' is
             indeed a prefix of a builtin library search path,
             prefix2 is substituted.  The error may appear if
             components are not found, or are too long.  See
             "PERLLIB_PREFIX" in README.os2.
    
         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 sighandlers, see the
             Signals entry in the perlipc manpage.  See also "Process
             terminated by SIGTERM/SIGINT" in README.os2.
    
    
    

    BUGS

         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
         Page.
    
         If you believe you have an unreported bug, please run the
         perlbug program included with your release.  Make sure you
         trim your bug down to a tiny but sufficient test case.  Your
         bug report, along with the output of `perl -V', will be sent
         off to <perlbug@perl.com> to be analysed by the Perl porting
         team.
    
    
    

    SEE ALSO

         The Changes file for exhaustive details on what changed.
    
         The INSTALL file for how to build Perl.  This file has been
         significantly updated for 5.004, so even veteran users
         should look through it.
    
         The README file for general stuff.
    
         The Copying file for copyright information.
    
    
    

    HISTORY

         Constructed by Tom Christiansen, grabbing material with
         permission from innumerable contributors, with kibitzing by
         more than a few Perl porters.
    
         Last update: Wed May 14 11:14:09 EDT 1997
    
    
    
    


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