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

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

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

NNAAMMEE #

 perl5004delta - what's new for perl5.004

DDEESSCCRRIIPPTTIIOONN #

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

SSuuppppoorrtteedd EEnnvviirroonnmmeennttss 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.

CCoorree CChhaannggeess Most importantly, many bugs were fixed, including several security problems. See the _C_h_a_n_g_e_s file in the distribution for details.

LLiisstt aassssiiggnnmmeenntt ttoo %%EENNVV wwoorrkkss “%ENV = ()” and “%ENV = @list” now work as expected (except on VMS where it generates a fatal error).

CChhaannggee ttoo “"CCaann’’tt llooccaattee FFoooo..ppmm iinn @@IINNCC"” eerrrroorr The error “Can’t locate Foo.pm in @INC” now lists the contents of @INC for easier debugging.

CCoommppiillaattiioonn ooppttiioonn:: BBiinnaarryy ccoommppaattiibbiilliittyy wwiitthh 55..000033 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.

$$PPEERRLL55OOPPTT eennvviirroonnmmeenntt vvaarriiaabbllee 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: --[[DDIIMMUUddmmww]].

LLiimmiittaattiioonnss oonn --MM,, --mm,, aanndd --TT ooppttiioonnss 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 --TT 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 --TT 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 --TT being found on the command line
 before it is found on the "#!" line.

MMoorree pprreecciissee wwaarrnniinnggss If you removed the --ww 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.

DDeepprreeccaatteedd:: IInnhheerriitteedd “"AAUUTTOOLLOOAADD"” ffoorr nnoonn--mmeetthhooddss 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.

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

SSuubbrroouuttiinnee aarrgguummeennttss ccrreeaatteedd oonnllyy wwhheenn tthheeyy’’rree mmooddiiffiieedd 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).

GGrroouupp vveeccttoorr cchhaannggeeaabbllee wwiitthh $$)) 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).

FFiixxeedd ppaarrssiinngg ooff $$$$<<ddiiggiitt>>,, &&$$<<ddiiggiitt>>,, eettcc.. 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.

FFiixxeedd llooccaalliizzaattiioonn ooff $$<<ddiiggiitt>>,, $$&&,, eettcc.. 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.

NNoo rreesseettttiinngg ooff $$.. oonn iimmpplliicciitt cclloossee The documentation for Perl 5.0 has always stated that $. is _n_o_t 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 _d_i_d reset $. under that circumstance; Perl 5.004 does not.

“"wwaannttaarrrraayy"” mmaayy rreettuurrnn uunnddeeff 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.

“"eevvaall EEXXPPRR"” ddeetteerrmmiinneess vvaalluuee ooff EEXXPPRR iinn ssccaallaarr ccoonntteexxtt 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".

CChhaannggeess ttoo ttaaiinnttiinngg cchheecckkss 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 gglloobb(()) 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).

NNeeww OOppccooddee mmoodduullee aanndd rreevviisseedd SSaaffee mmoodduullee 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.

EEmmbbeeddddiinngg iimmpprroovveemmeennttss 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.

IInntteerrnnaall cchhaannggee:: FFiilleeHHaannddllee ccllaassss bbaasseedd oonn IIOO:::: ccllaasssseess 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}.

IInntteerrnnaall cchhaannggee:: PPeerrllIIOO aabbssttrraaccttiioonn iinntteerrffaaccee It is now possible to build Perl with AT&T’s sfio IO package instead of stdio. See perlapio for more details, and the _I_N_S_T_A_L_L file for how to use it.

NNeeww aanndd cchhaannggeedd ssyynnttaaxx $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)".

NNeeww aanndd cchhaannggeedd bbuuiillttiinn ccoonnssttaannttss

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 _n_o_t interpolate into
     strings.

NNeeww aanndd cchhaannggeedd bbuuiillttiinn vvaarriiaabblleess $^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 ddiiee(())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
     _I_N_S_T_A_L_L 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.

NNeeww aanndd cchhaannggeedd bbuuiillttiinn ffuunnccttiioonnss 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 sspprriinnttff(()) 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 sspprriinnttff(()) 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 "sprintf" in perlfunc 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).

 mmyy(()) in Control Structures
     You can now use mmyy(()) (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 mmyy(()) on global punctuation variables
     such as $_ and the like.

 ppaacckk(()) and uunnppaacckk(())
     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 ppaacckk(()) and uunnppaacckk(()) now fail when their templates contain
     invalid types.  (Invalid types used to be ignored.)

 ssyysssseeeekk(())
     The new ssyysssseeeekk(()) operator is a variant of sseeeekk(()) that sets and gets
     the file's system read/write position, using the llsseeeekk(2) system
     call.  It is the only reliable way to seek before using ssyyssrreeaadd(()) or
     ssyysswwrriittee(()).  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 perlfunc.

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

 "m//x" ignores whitespace before ?*+{}
     The "m//x" construct has always been intended to ignore all unescaped
     whitespace.  However, before Perl 5.004, whitespace had the effect of
     escaping repeat modifiers like "*" or "?"; for 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
         .

NNeeww bbuuiillttiinn mmeetthhooddss The “UNIVERSAL” package automatically contains the following methods that are inherited by all other classes:

 isa(CLASS)
     "isa" returns _t_r_u_e 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
     _u_n_d_e_f 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); #

 NNOOTTEE:: "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.

TTIIEEHHAANNDDLLEE nnooww ssuuppppoorrtteedd See perltie for other kinds of ttiiee(())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";
         }

MMaalllloocc eennhhaanncceemmeennttss 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 mmaalllloocc(()).)

-DPERL_EMERGENCY_SBRK #

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

-DPACK_MALLOC #

     Perl memory allocation is by bucket with sizes close to powers of
     two.  Because of these malloc overhead 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.

MMiisscceellllaanneeoouuss eeffffiicciieennccyy eennhhaanncceemmeennttss 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.

SSuuppppoorrtt ffoorr MMoorree OOppeerraattiinngg SSyysstteemmss Support for the following operating systems is new in Perl 5.004.

WWiinn3322 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 ExtUtils::MakeMaker and h2xs, so that many extensions available on the Comprehensive Perl Archive Network (CPAN) can now be readily built under Windows NT. See http://www.perl.com/ for more information on CPAN and _R_E_A_D_M_E_._w_i_n_3_2 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 _R_E_A_D_M_E_._c_y_g_w_i_n_3_2 in the perl
 distribution for more details on this port and how to obtain the Cygwin32
 toolkit.

PPllaann 99 See _R_E_A_D_M_E_._p_l_a_n_9 in the perl distribution.

QQNNXX #

 See _R_E_A_D_M_E_._q_n_x in the perl distribution.

AAmmiiggaaOOSS See _R_E_A_D_M_E_._a_m_i_g_a_o_s in the perl distribution.

PPrraaggmmaattaa 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 _'_b_l_i_b_' directory structure starting in _d_i_r
     (or current directory) and working back up to five levels of parent
     directories.

     Intended for use on command line with --MM 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 "Constant Functions" in perlsub.

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

     When "use locale" is in effect, the current LC_CTYPE locale is used
     for regular expressions and case mapping; LC_COLLATE for string
     ordering; and LC_NUMERIC for numeric formatting in printf and sprintf
     (but nnoott 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 PPOOSSIIXX::::sseettllooccaallee(()).

     See perllocale 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.

MMoodduulleess RReeqquuiirreedd UUppddaatteess 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.

IInnssttaallllaattiioonn ddiirreeccttoorriieess The _i_n_s_t_a_l_l_p_e_r_l 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.

MMoodduullee iinnffoorrmmaattiioonn ssuummmmaarryy 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

FFccnnttll 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 ssyyssooppeenn(())
 and ffccnnttll(()) 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 ffccnnttll(()) and ooppeenn(()).

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

LOCK_SH LOCK_EX LOCK_NB LOCK_UN #

 These constants are defined in all environments (because where there is
 no fflloocckk(()) 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'").

IIOO #

 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.

MMaatthh::::CCoommpplleexx 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

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

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

 •   Fixed a handful of bugs.

 •   By public demand, added support for the standard hash function
     eexxiissttss(()).

 •   Made it compatible with Berkeley DB 1.86.

 •   Made negative subscripts work with RECNO interface.

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

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

 •   Updated documentation.

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

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

OObbjjeecctt--oorriieenntteedd oovveerrrriiddeess ffoorr bbuuiillttiinn ooppeerraattoorrss 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);

UUttiilliittyy CChhaannggeess ppoodd22hhttmmll Sends converted HTML to standard output The _p_o_d_2_h_t_m_l 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 _p_o_d_2_h_t_m_l did. Use the -–-oouuttffiillee==FFIILLEENNAAMMEE option to write to a file.

xxssuubbpppp “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, _x_s_u_b_p_p 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 _x_s_u_b_p_p finds what looks like an
     assignment to ST(0), it assumes that the XSUB's return type is really

“SV *”. #

CC LLaanngguuaaggee AAPPII CChhaannggeess “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 _s_e_c_o_n_d 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
     perlguts, perlembed and perlcall 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 perlguts for details.

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

 perldelta
     This document.

 perlfaq
     Frequently asked questions.

 perllocale
     Locale support (internationalization and localization).

 perltoot
     Tutorial on Perl OO programming.

 perlapio
     Perl internal IO abstraction interface.

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

 perldebug
     Although not new, this has been massively updated.

 perlsec
     Although not new, this has been massively updated.

NNeeww DDiiaaggnnoossttiiccss 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 ddeelleettee(()) 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 "grep" in perlfunc and "map" in perlfunc for
     alternatives.

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

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

 Bareword "%s" refers to nonexistent package
     (W) You used a qualified bareword of the form "Foo::", but the
     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 perlref.

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

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

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

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

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

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

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

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

«EOF;"). #

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

 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
     "sprintf" in perlfunc.

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

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

 Name "%s::%s" used only once: possible typo
     (W) Typographical errors often show up as unique variable names.  If
     you had a good reason for having a unique name, then just 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 perlform.

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

 Out of memory!
     (X|F) The mmaalllloocc(()) 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 ddiiee(())ing with this message.  In
     this case the error is trappable _o_n_c_e.

 Out of memory during request for %s
     (F) The mmaalllloocc(()) 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 ffrreexxpp(()) failed, making printf("%f")
     impossible.

 Possible attempt to put comments in qqww(()) list
     (W) qqww(()) 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) qqww(()) 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.

 Stub found while resolving method `%s' overloading `%s' in %s
     (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 "--TT" option
     (X) The #! line (or local equivalent) in a Perl script contains the
     --TT option, but Perl was not invoked with --TT in its argument list.
     This is an error because, by the time Perl discovers a --TT 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 ddeeffiinneedd(())
     (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) _a_n_o_n_y_m_o_u_s subroutine is inside a _n_a_m_e_d
     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) _n_a_m_e_d 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 _n_e_v_e_r 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 wwaarrnn(()) 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 _R_E_A_D_M_E_._o_s_2.

 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 _R_E_A_D_M_E_._o_s_2.

 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 "Signals" in perlipc.  See also "Process terminated by
     SIGTERM/SIGINT" in _R_E_A_D_M_E_._o_s_2.

BBUUGGSS #

 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 ppeerrllbbuugg 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 <_p_e_r_l_b_u_g_@_p_e_r_l_._c_o_m> to be analysed by the
 Perl porting team.

SSEEEE AALLSSOO #

 The _C_h_a_n_g_e_s file for exhaustive details on what changed.

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

 The _R_E_A_D_M_E file for general stuff.

 The _C_o_p_y_i_n_g file for copyright information.

HHIISSTTOORRYY #

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

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

perl v5.36.3 2019-02-13 PERL5004DELTA(1)