X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperldelta.pod;h=4ec71c8eb55ae8e51be7af4b985d529df28c4289;hb=f4dad39ef1a76c1f6bbf6733d7c2ee209381be78;hp=d202e70e56fb3366aaa9ccf49363566d6dde6dcf;hpb=a61fe43df197fcc70e6f310c06ee17d52b606c45;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perldelta.pod b/pod/perldelta.pod index d202e70..4ec71c8 100644 --- a/pod/perldelta.pod +++ b/pod/perldelta.pod @@ -1,1030 +1,27 @@ =head1 NAME -perldelta - what's new for perl5.004 +perldelta - what's new for perl5.005 =head1 DESCRIPTION -This document describes differences between the 5.003 release (as -documented in I, second edition--the Camel Book) and -this one. +This document describes differences between the 5.004 release and this one. -=head1 Supported Environments - -Perl5.004 builds out of the box on Unix, Plan9, LynxOS, VMS, OS/2, -QNX, and AmigaOS. +=head1 Incompatible Changes =head1 Core Changes -Most importantly, many bugs were fixed. See the F -file in the distribution for details. - -=head2 Compilation Option: Binary Compatibility With 5.003 - -There is a new Configure question that asks if you want to maintain -binary compatibility with Perl 5.003. If you choose binary -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. - -=head2 New Opcode Module and Revised Safe Module - -A new Opcode module supports the creation, manipulation and -application of opcode masks. The revised Safe module has a new API -and is implemented using the new Opcode module. Please read the new -Opcode and Safe documentation. - -=head2 Fixed Parsing of $$, &$, etc. - -A bug in previous versions of Perl 5.0 prevented proper parsing of -numeric special variables as symbolic references. That bug has been -fixed. As a result, the string "$$0" is no longer equivalent to -C<$$."0">, but rather to C<${$0}>. To get the old behavior, change -"$$" followed by a digit to "${$}". - -=head2 Internal Change: FileHandle Deprecated - -Filehandles are now stored internally as type IO::Handle. -Although C and C<*STDOUT{FILEHANDLE}> -are still supported for backwards compatibility, -C (or C or C) and -C<*STDOUT{IO}> are the way of the future. - -=head2 Internal Change: PerlIO internal IO abstraction interface - -It is now possible to build Perl with AT&T's sfio IO package -instead of stdio. See L for more details, and -the F file for how to use it. - -=head2 New and Changed Built-in Variables - -=over - -=item $^E - -Extended error message on some platforms. (Also known as -$EXTENDED_OS_ERROR if you C). - -=item $^H - -The current set of syntax checks enabled by C. See the -documentation of C for more details. Not actually new, but -newly documented. -Because it is intended for internal use by Perl core components, -there is no C long name for this variable. - -=item $^M - -By default, running out of memory it is not trappable. However, if -compiled for this, Perl may use the contents of C<$^M> as an emergency -pool after die()ing with this message. Suppose that your Perl were -compiled with -DEMERGENCY_SBRK and used Perl's malloc. Then - - $^M = 'a' x (1<<16); - -would allocate a 64K buffer for use when in emergency. -See the F file for information on how to enable this option. -As a disincentive to casual use of this advanced feature, -there is no C long name for this variable. - -=back - -=head2 New and Changed Built-in Functions - -=over - -=item delete on slices - -This now works. (e.g. C) - -=item flock - -is now supported on more platforms, and prefers fcntl -to lockf when emulating. - -=item printf and sprintf - -now support "%i" as a synonym for "%d", and the "h" modifier. -So "%hi" means "short integer in decimal", and "%ho" means -"unsigned short integer as octal". - -=item keys as an lvalue - -As an lvalue, C 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 C<%hash> will have at least 200 buckets allocated for it. These -buckets will be retained even if you do C<%hash = ()>; use C if you want to free the storage while C<%hash> is still in scope. -You can't shrink the number of buckets allocated for the hash using -C in this way (but you needn't worry about doing this by accident, -as trying has no effect). - -=item 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 $answer = ) =~ /^y(es)?$/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. - -=item unpack() and pack() - -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. - -=item use VERSION - -If the first argument to C 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 C occurs at compile time, this check happens -immediately during the compilation process, unlike C, -which waits until run-time for the check. This is often useful if you -need to check the current Perl version before Cing library modules -which have changed in incompatible ways from older versions of Perl. -(We try not to do this more than we have to.) - -=item use Module VERSION LIST - -If the VERSION argument is present between Module and LIST, then the -C 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. - -=item prototype(FUNCTION) - -Returns the prototype of a function as a string (or C 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.) - -=item $_ as Default - -Functions documented in the Camel to default to $_ now in -fact do, and all those that do are so documented in L. - -=item C does not trigger a pos() reset on failure - -The C match iteration construct used to reset the iteration -when it failed to match (so that the next C match would start at -the beginning of the string). You now have to explicitly do a -C to reset the "last match" position, or modify the -string in some way. This change makes it practical to chain C -matches together in conjunction with ordinary matches using the C<\G> -zero-width assertion. See L and L. - -=item nested C closures work now - -Prior to the 5.004 release, nested anonymous functions -didn't work right. They do now. - -=item formats work right on changing lexicals - -Just like anonymous functions that contain lexical variables -that change (like a lexical index variable for a C loop), -formats now work properly. For example, this silently failed -before, and is fine now: - - my $i; - foreach $i ( 1 .. 10 ) { - format = - my i is @# - $i - . - write; - } - -=back - -=head2 New Built-in Methods - -The C package automatically contains the following methods that -are inherited by all other classes: - -=over - -=item isa(CLASS) - -C returns I if its object is blessed into a sub-class of C - -C is also exportable and can be called as a sub with two arguments. This -allows the ability to check what a reference points to. Example: - - use UNIVERSAL qw(isa); - - if(isa($ref, 'ARRAY')) { - ... - } - -=item can(METHOD) - -C checks to see if its object has a method called C, -if it does then a reference to the sub is returned; if it does not then -I is returned. - -=item VERSION( [NEED] ) - -C 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 -C form of C. - - use A 1.2 qw(some imported subs); - # implies: - A->VERSION(1.2); - -=back - -B C directly uses Perl's internal code for method lookup, and -C 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 C in order to make these methods -available to your program. This is necessary only if you wish to -have C available as a plain subroutine in the current package. - -=head2 TIEHANDLE Now Supported - -See L for other kinds of tie()s. - -=over - -=item TIEHANDLE classname, LIST - -This is the constructor for the class. That means it is expected to -return an object of some sort. The reference can be used to -hold some internal information. - - sub TIEHANDLE { - print "\n"; - my $i; - return bless \$i, shift; - } - -=item 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; - $$r++; - return print join( $, => map {uc} @_), $\; - } - -=item READLINE this - -This method will be called when the handle is read from. The method -should return undef when there is no more data. - - sub READLINE { - $r = shift; - return "PRINT called $$r times\n"; - } - -=item DESTROY this - -As with the other types of ties, this method will be called when the -tied handle is about to be destroyed. This is useful for debugging and -possibly for cleaning up. - - sub DESTROY { - print "\n"; - } - -=back - -=head2 Malloc Enhancements - -If perl's malloc() is used, you can print memory statistics at runtime -by running Perl thusly: - - env PERL_DEBUG_MSTATS=2 perl your_script_here - -The value of 2 means to print statistics after compilation and on -exit; with a value of 1, the statistics ares printed only on exit. -(If you want the statistics at an arbitrary time, you'll need to -install the optional module Devel::Peek.) - -In addition, three new compilation flags are recognized by malloc.c. -(They have no effect if perl is compiled with system malloc().) - -=over - -=item -DEMERGENCY_SBRK - -If this macro is defined, running out of memory need not be a fatal -error: a memory pool can allocated by assigning to the special -variable C<$^M>. See L<"$^M">. - -=item -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 C 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 C) 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). - -=item -DTWO_POT_OPTIMIZE - -Similarly to C, 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. - -=back - -=head2 Miscellaneous Efficiency Enhancements - -Functions that have an empty prototype and that do nothing but return -a fixed value are now inlined (e.g. C). - -Each unique hash key is only allocated once, no matter how many hashes -have an entry with that key. So even if you have 100 copies of the -same hash, the hash keys never have to be re-allocated. - -=head1 Pragmata - -Four new pragmatic modules exist: - -=over - -=item use blib - -=item use blib 'dir' - -Looks for MakeMaker-like I<'blib'> directory structure starting in -I (or current directory) and working back up to five levels of -parent directories. - -Intended for use on command line with B<-M> option as a way of testing -arbitrary scripts against an uninstalled version of a package. - -=item use locale - -Tells the compiler to enable (or disable) the use of POSIX locales for -built-in operations. - -When C 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 B in print). LC_NUMERIC is always used in write, since -lexical scoping of formats is problematic at best. - -Each C or C 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::setlocale(). - -See L for more information. - -=item use ops - -Disable unsafe opcodes, or any named opcodes, when compiling Perl code. - -=item use vmsish - -Enable VMS-specific language features. Currently, there are three -VMS-specific features available: 'status', which makes C<$?> and -C return genuine VMS status values instead of emulating POSIX; -'exit', which makes C take a genuine VMS status value instead of -assuming that C is an error; and 'time', which makes all times -relative to the local time zone, in the VMS tradition. - -=back - =head1 Modules -=head2 Installation Directories - -The I 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. - -=head2 Fcntl - -New constants in the existing Fcntl modules are now supported, -provided that your operating system happens to support them: - - F_GETOWN F_SETOWN - O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC - O_EXLOCK O_SHLOCK - -These constants are intended for use with the Perl operators sysopen() -and fcntl() and the basic database modules like SDBM_File. For the -exact meaning of these and other Fcntl constants please refer to your -operating system's documentation for fcntl() and open(). - -In addition, the Fcntl module now provides these constants for use -with the Perl operator flock(): - - LOCK_SH LOCK_EX LOCK_NB LOCK_UN - -These constants are defined in all environments (because where there is -no flock() system call, Perl emulates it). However, for historical -reasons, these constants are not exported unless they are explicitly -requested with the ":flock" tag (e.g. C). - -=head2 Module Information Summary - -Brand new modules, arranged by topic rather than strictly -alphabetically: - - CPAN interface to Comprehensive Perl Archive Network - CPAN::FirstTime create a CPAN configuration file - CPAN::Nox run CPAN while avoiding compiled extensions - - 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/Template.pm Structure/member template builder - File/stat.pm Object-oriented wrapper around CORE::stat - Net/hostent.pm Object-oriented wrapper around CORE::gethost* - Net/netent.pm Object-oriented wrapper around CORE::getnet* - Net/protoent.pm Object-oriented wrapper around CORE::getproto* - Net/servent.pm Object-oriented wrapper around CORE::getserv* - Time/gmtime.pm Object-oriented wrapper around CORE::gmtime - Time/localtime.pm Object-oriented wrapper around CORE::localtime - Time/tm.pm Perl implementation of "struct tm" for {gm,local}time - User/grent.pm Object-oriented wrapper around CORE::getgr* - User/pwent.pm Object-oriented wrapper around CORE::getpw* - - Tie/RefHash.pm Base class for tied hashes with references as keys - - UNIVERSAL.pm Base class for *ALL* classes - -=head2 IO - -The IO module provides a simple mechanism to load all of 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. - -=head2 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) +=head2 Required Updates -And these functions are now exported: - - pi i Re Im arg - log10 logn cbrt root - tan cotan asin acos atan acotan - sinh cosh tanh cotanh asinh acosh atanh acotanh - cplx cplxe - -=head2 DB_File - -There have been quite a few changes made to DB_File. Here are a few of -the highlights: - -=over - -=item * - -Fixed a handful of bugs. - -=item * - -By public demand, added support for the standard hash function exists(). - -=item * - -Made it compatible with Berkeley DB 1.86. - -=item * - -Made negative subscripts work with RECNO interface. - -=item * - -Changed the default flags from O_RDWR to O_CREAT|O_RDWR and the default -mode from 0640 to 0666. - -=item * - -Made DB_File automatically import the open() constants (O_RDWR, -O_CREAT etc.) from Fcntl, if available. - -=item * - -Updated documentation. - -=back - -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. - -=head2 Net::Ping - -Major rewrite - support added for both udp echo and real icmp pings. - -=head2 Overridden Built-ins - -Many of the Perl built-ins 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); + XXX Any??? =head1 Utility Changes -=head2 xsubpp - -=over - -=item C XSUBs now default to returning nothing - -Due to a documentation/implementation bug in previous versions of -Perl, XSUBs with a return type of C 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 C, 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 C. - -For backward compatibility, I tries to guess whether a -C XSUB is really C or if it wants to return an C. -It does so by examining the text of the XSUB: if I finds -what looks like an assignment to C, it assumes that the -XSUB's return type is really C. - -=back - =head1 C Language API Changes -=over - -=item C and C - -The C 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 C. -Instead, you should use the C macro on the GV to extract its CV, -and pass the CV to C. - -The most likely symptom of passing the result of C to -C is Perl's producing an "Undefined subroutine called" -error on the I call to a given method (since there is no cache -on the first call). - -=item Extended API for manipulating hashes - -Internal handling of hash keys has changed. The old hashtable API -is still fully supported, and will likely remain that way. The additions -to the API allow passing keys as Cs, so that C hashes can be -given real scalars as keys rather than plain strings (non-tied hashes still -can only use strings as keys). All new extensions must use the new -hash access functions and macros if they wish to use C keys. These -additions also make it feasible to manipulate whole Cs (hash entries), -allowing for more efficient handling of hash data. See L for -details. - -=back - =head1 Documentation Changes -Many of the base and library pods were updated. These -new pods are included in section 1: - -=over - -=item L - -A "howto" on reporting perl bugs. - -=item L - -This document. - -=item L - -Locale support (internationalization and localization). - -=item L - -Tutorial on Perl OO programming. - -=item L - -Perl internal IO abstraction interface. - -=item L - -Although not new, this has been massively updated. - -=item L - -Although not new, this has been massively updated. - -=back - -=head1 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 (non-trappable). - (A) An alien error message (not generated by Perl). - -=over - -=item "my" variable %s masks earlier declaration in same scope - -(S) 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. - -=item %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"} - -=item Allocation too large: %lx - -(X) You can't allocate more than 64K on an MSDOS machine. - -=item Allocation too large - -(F) You can't allocate more than 2^31+"small amount" bytes. - -=item Attempt to free non-existent shared string - -(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. - -=item 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 L. - -=item Unsupported function fork - -(F) Your version of executable does not support forking. - -Note that under some systems, like OS/2, there may be different flavors of -Perl executables, some of which may support fork, some not. Try changing -the name you call Perl by to C, C, and so on. - -=item Ill-formed logical name |%s| in prime_env_iter - -(W) A warning peculiar to VMS. A logical name was encountered when preparing -to iterate over %ENV which violates the syntactic rules governing logical -names. Since it cannot be translated normally, it is skipped, and will not -appear in %ENV. This may be a benign occurrence, as some software packages -might directly modify logical name tables and introduce non-standard names, -or it may indicate that a logical name table has been corrupted. - -=item Can't use bareword ("%s") as %s ref while "strict refs" in use - -(F) Only hard references are allowed by "strict refs". Symbolic references -are disallowed. See L. - -=item Constant subroutine %s redefined - -(S) You redefined a subroutine which had previously been eligible for -inlining. See L for commentary and -workarounds. - -=item Died - -(F) You passed die() an empty string (the equivalent of C) or -you called it with no args and both C<$@> and C<$_> were empty. - -=item 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. - -=item 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. - -=item 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 C pragma is -provided for just this purpose). - -=item 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 L. - -=item 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 Cing past the buffer -will extend the buffer and zero pad the new area. - -=item Stub found while resolving method `%s' overloading `%s' in package `%s' - -(P) Overloading resolution over @ISA tree may be broken by importing stubs. -Stubs should never be implicitely created, but explicit calls to C -may break this. - -=item Cannot resolve method `%s' overloading `%s' in package `s' - -(P) Internal error trying to resolve overloading specified by a method -name (as opposed to a subroutine reference). - -=item Out of memory! - -(X|F) The malloc() function returned 0, indicating there was insufficient -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 C<$^M> as -an emergency pool after die()ing with this message. In this case the -error is trappable I. - -=item 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. - -=item 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 -exclamation marks 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 - ); - -=item 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 !; - -=item Scalar value @%s{%s} better written as $%s{%s} - -(W) You've used a hash slice (indicated by @) to select a single element of -a hash. Generally it's better to ask for a scalar value (indicated by $). -The difference is that C<$foo{&bar}> always behaves like a scalar, both when -assigning to it and when evaluating its argument, while C<@foo{&bar}> behaves -like a list when you assign to it, and provides a list context to its -subscript, which can do weird things if you're expecting only one subscript. - -=item untie attempted while %d inner references still exist - -(W) A copy of the object returned from C (or C) was still -valid when C was called. - -=item Value of %s construct can be "0"; test with defined() - -(W) In a conditional expression, you used , <*> (glob), or -C as a boolean value. Each of these constructs can return a -value of "0"; that would make the conditional expression false, which -is probably not what you intended. When using these constructs in -conditional expressions, test their values with the C operator. - -=item Variable "%s" may be unavailable - -(W) An inner (nested) I subroutine is inside a I -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 { $a } } } - -If the anonymous subroutine is called or referenced (directly or -indirectly) from the outermost subroutine, it will share the variable -as you would expect. But if the anonymous subroutine is called or -referenced when the outermost subroutine is not active, it will see -the value of the shared variable as it was before and during the -*first* call to the outermost subroutine, which is probably not what -you want. - -In these circumstances, it is usually best to make the middle -subroutine anonymous, using the C syntax. Perl has specific -support for shared variables in nested anonymous subroutines; a named -subroutine in between interferes with this feature. - -=item Variable "%s" will not stay shared - -(W) An inner (nested) I subroutine is referencing a lexical -variable defined in an outer subroutine. - -When the inner subroutine is called, it will probably see the value of -the outer subroutine's variable as it was before and during the -*first* call to the outer subroutine; in this case, after the first -call to the outer subroutine is complete, the inner and outer -subroutines will no longer share a common value for the variable. In -other words, the variable will no longer be shared. - -Furthermore, if the outer subroutine is anonymous and references a -lexical variable outside itself, then the outer and inner subroutines -will I share the given variable. - -This problem can usually be solved by making the inner subroutine -anonymous, using the C syntax. When inner anonymous subs that -reference variables in outer subroutines are called or referenced, -they are automatically re-bound to the current values of such -variables. - -=item Warning: something's wrong - -(W) You passed warn() an empty string (the equivalent of C) or -you called it with no args and C<$_> was empty. - -=item 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. - -=item Malformed PERLLIB_PREFIX - -(F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form - - prefix1;prefix2 - -or - - prefix1 prefix2 - -with non-empty prefix1 and prefix2. If C is indeed a prefix of -a builtin library search path, prefix2 is substituted. The error may appear -if components are not found, or are too long. See L. - -=item PERL_SH_DIR too long - -(F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the -C-shell in. See L. - -=item Process terminated by SIG%s - -(W) This is a standard message issued by OS/2 applications, while *nix -applications die in silence. It is considered a feature of the OS/2 -port. One can easily disable this by appropriate sighandlers, see -L. See L. - -=back - =head1 BUGS If you find what you think is a bug, you might check the headers of @@ -1033,27 +30,19 @@ There may also be information at http://www.perl.com/perl/, the Perl Home Page. If you believe you have an unreported bug, please run the B -program included with your release. Make sure you trim your bug -down to a tiny but sufficient test case. Your bug report, along -with the output of C, will be sent off to perlbug@perl.com -to be analysed by the Perl porting team. +program included with your release. Make sure you trim your bug down +to a tiny but sufficient test case. Your bug report, along with the +output of C, will be sent off to > to be +analysed by the Perl porting team. =head1 SEE ALSO The F file for exhaustive details on what changed. -The F file for how to build Perl. This file has been -significantly updated for 5.004, so even veteran users should -look through it. +The F file for how to build Perl. The F file for general stuff. -The F file for copyright information. +The F and F files for copyright information. =head1 HISTORY - -Constructed by Tom Christiansen, grabbing material with permission -from innumerable contributors, with kibitzing by more than a few Perl -porters. - -Last update: Tue Jan 14 14:03:02 EST 1997