PERL5100DELTA(1) Perl Programmers Reference Guide PERL5100DELTA(1) #
PERL5100DELTA(1) Perl Programmers Reference Guide PERL5100DELTA(1)
NNAAMMEE #
perl5100delta - what is new for perl 5.10.0
DDEESSCCRRIIPPTTIIOONN #
This document describes the differences between the 5.8.8 release and the
5.10.0 release.
Many of the bug fixes in 5.10.0 were already seen in the 5.8.X
maintenance releases; they are not duplicated here and are documented in
the set of man pages named perl58[1-8]?delta.
CCoorree EEnnhhaanncceemmeennttss TThhee “"ffeeaattuurree"” pprraaggmmaa The “feature” pragma is used to enable new syntax that would break Perl’s backwards-compatibility with older releases of the language. It’s a lexical pragma, like “strict” or “warnings”.
Currently the following new features are available: "switch" (adds a
switch statement), "say" (adds a "say" built-in function), and "state"
(adds a "state" keyword for declaring "static" variables). Those features
are described in their own sections of this document.
The "feature" pragma is also implicitly loaded when you require a minimal
perl version (with the "use VERSION" construct) greater than, or equal
to, 5.9.5. See feature for details.
NNeeww --EE ccoommmmaanndd--lliinnee sswwiittcchh --EE is equivalent to --ee, but it implicitly enables all optional features (like “use feature “:5.10"”).
DDeeffiinneedd--oorr ooppeerraattoorr A new operator “//” (defined-or) has been implemented. The following expression:
$a // $b
is merely equivalent to
defined $a ? $a : $b
and the statement
$c //= $d;
can now be used instead of
$c = $d unless defined $c;
The "//" operator has the same precedence and associativity as "||".
Special care has been taken to ensure that this operator Do What You Mean
while not breaking old code, but some edge cases involving the empty
regular expression may now parse differently. See perlop for details.
SSwwiittcchh aanndd SSmmaarrtt MMaattcchh ooppeerraattoorr Perl 5 now has a switch statement. It’s available when “use feature ‘switch’” is in effect. This feature introduces three new keywords, “given”, “when”, and “default”:
given ($foo) {
when (/^abc/) { $abc = 1; }
when (/^def/) { $def = 1; }
when (/^xyz/) { $xyz = 1; }
default { $nothing = 1; }
}
A more complete description of how Perl matches the switch variable
against the "when" conditions is given in "Switch statements" in perlsyn.
This kind of match is called _s_m_a_r_t _m_a_t_c_h, and it's also possible to use
it outside of switch statements, via the new "~~" operator. See "Smart
matching in detail" in perlsyn.
This feature was contributed by Robin Houston.
RReegguullaarr eexxpprreessssiioonnss Recursive Patterns It is now possible to write recursive patterns without using the “(??{})” construct. This new way is more efficient, and in many cases easier to read.
Each capturing parenthesis can now be treated as an independent
pattern that can be entered by using the "(?PARNO)" syntax ("PARNO"
standing for "parenthesis number"). For example, the following
pattern will match nested balanced angle brackets:
/
^ # start of line
( # start capture buffer 1
< # match an opening angle bracket
(?: # match one of:
(?> # don't backtrack over the inside of this group
[^<>]+ # one or more non angle brackets
) # end non backtracking group
| # ... or ...
(?1) # recurse to bracket 1 and try it again
)* # 0 or more times.
> # match a closing angle bracket
) # end capture buffer one
$ # end of line
/x
PCRE users should note that Perl's recursive regex feature allows
backtracking into a recursed pattern, whereas in PCRE the recursion
is atomic or "possessive" in nature. As in the example above, you
can add (?>) to control this selectively. (Yves Orton)
Named Capture Buffers
It is now possible to name capturing parenthesis in a pattern and
refer to the captured contents by name. The naming syntax is
"(?<NAME>....)". It's possible to backreference to a named buffer
with the "\k<NAME>" syntax. In code, the new magical hashes "%+" and
"%-" can be used to access the contents of the capture buffers.
Thus, to replace all doubled chars with a single copy, one could
write
s/(?<letter>.)\k<letter>/$+{letter}/g
Only buffers with defined contents will be "visible" in the "%+"
hash, so it's possible to do something like
foreach my $name (keys %+) {
print "content of buffer '$name' is $+{$name}\n";
}
The "%-" hash is a bit more complete, since it will contain array
refs holding values from all capture buffers similarly named, if
there should be many of them.
"%+" and "%-" are implemented as tied hashes through the new module
"Tie::Hash::NamedCapture".
Users exposed to the .NET regex engine will find that the perl
implementation differs in that the numerical ordering of the buffers
is sequential, and not "unnamed first, then named". Thus in the
pattern
/(A)(?B)(C)(?D)/
#
$1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D' and
not $1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET
programmer would expect. This is considered a feature. :-) (Yves
Orton)
Possessive Quantifiers
Perl now supports the "possessive quantifier" syntax of the "atomic
match" pattern. Basically a possessive quantifier matches as much as
it can and never gives any back. Thus it can be used to control
backtracking. The syntax is similar to non-greedy matching, except
instead of using a '?' as the modifier the '+' is used. Thus "?+",
"*+", "++", "{min,max}+" are now legal quantifiers. (Yves Orton)
Backtracking control verbs
The regex engine now supports a number of special-purpose backtrack
control verbs: (*THEN), (*PRUNE), (*MARK), (*SKIP), (*COMMIT),
(*FAIL) and (*ACCEPT). See perlre for their descriptions. (Yves
Orton)
Relative backreferences
A new syntax "\g{N}" or "\gN" where "N" is a decimal integer allows a
safer form of back-reference notation as well as allowing relative
backreferences. This should make it easier to generate and embed
patterns that contain backreferences. See "Capture buffers" in
perlre. (Yves Orton)
"\K" escape
The functionality of Jeff Pinyan's module Regexp::Keep has been added
to the core. In regular expressions you can now use the special
escape "\K" as a way to do something like floating length positive
lookbehind. It is also useful in substitutions like:
s/(foo)bar/$1/g
that can now be converted to
s/foo\Kbar//g
which is much more efficient. (Yves Orton)
Vertical and horizontal whitespace, and linebreak
Regular expressions now recognize the "\v" and "\h" escapes that
match vertical and horizontal whitespace, respectively. "\V" and "\H"
logically match their complements.
"\R" matches a generic linebreak, that is, vertical whitespace, plus
the multi-character sequence "\x0D\x0A".
Optional pre-match and post-match captures with the /p flag
There is a new flag "/p" for regular expressions. Using this makes
the engine preserve a copy of the part of the matched string before
the matching substring to the new special variable "${^PREMATCH}",
the part after the matching substring to "${^POSTMATCH}", and the
matched substring itself to "${^MATCH}".
Perl is still able to store these substrings to the special variables
"$`", "$'", $&, but using these variables anywhere in the program
adds a penalty to all regular expression matches, whereas if you use
the "/p" flag and the new special variables instead, you pay only for
the regular expressions where the flag is used.
For more detail on the new variables, see perlvar; for the use of the
regular expression flag, see perlop and perlre.
“"ssaayy(())“” ssaayy(()) is a new built-in, only available when “use feature ‘say’” is in effect, that is similar to pprriinntt(()), but that implicitly appends a newline to the printed string. See “say” in perlfunc. (Robin Houston)
LLeexxiiccaall $$ The default variable $_ can now be lexicalized, by declaring it like any other lexical variable, with a simple
my $_;
The operations that default on $_ will use the lexically-scoped version
of $_ when it exists, instead of the global $_.
In a "map" or a "grep" block, if $_ was previously my'ed, then the $_
inside the block is lexical as well (and scoped to the block).
In a scope where $_ has been lexicalized, you can still have access to
the global version of $_ by using $::_, or, more simply, by overriding
the lexical declaration with "our $_". (Rafael Garcia-Suarez)
TThhee “”“” pprroottoottyyppee A new prototype character has been added. “” is equivalent to “$” but defaults to $ if the corresponding argument isn’t supplied (both “$” and “_” denote a scalar). Due to the optional nature of the argument, you can only use it at the end of a prototype, or before a semicolon.
This has a small incompatible consequence: the pprroottoottyyppee(()) function has
been adjusted to return "_" for some built-ins in appropriate cases (for
example, "prototype('CORE::rmdir')"). (Rafael Garcia-Suarez)
UUNNIITTCCHHEECCKK bblloocckkss “UNITCHECK”, a new special code block has been introduced, in addition to “BEGIN”, “CHECK”, “INIT” and “END”.
"CHECK" and "INIT" blocks, while useful for some specialized purposes,
are always executed at the transition between the compilation and the
execution of the main program, and thus are useless whenever code is
loaded at runtime. On the other hand, "UNITCHECK" blocks are executed
just after the unit which defined them has been compiled. See perlmod for
more information. (Alex Gough)
NNeeww PPrraaggmmaa,, “"mmrroo"” A new pragma, “mro” (for Method Resolution Order) has been added. It permits to switch, on a per-class basis, the algorithm that perl uses to find inherited methods in case of a multiple inheritance hierarchy. The default MRO hasn’t changed (DFS, for Depth First Search). Another MRO is available: the C3 algorithm. See mro for more information. (Brandon Black)
Note that, due to changes in the implementation of class hierarchy
search, code that used to undef the *ISA glob will most probably break.
Anyway, undef'ing *ISA had the side-effect of removing the magic on the
@ISA array and should not have been done in the first place. Also, the
cache *::ISA::CACHE:: no longer exists; to force reset the @ISA cache,
you now need to use the "mro" API, or more simply to assign to @ISA (e.g.
with "@ISA = @ISA").
rreeaaddddiirr(()) mmaayy rreettuurrnn aa “"sshhoorrtt ffiilleennaammee"” oonn WWiinnddoowwss The rreeaaddddiirr(()) function may return a “short filename” when the long filename contains characters outside the ANSI codepage. Similarly CCwwdd::::ccwwdd(()) may return a short directory name, and gglloobb(()) may return short names as well. On the NTFS file system these short names can always be represented in the ANSI codepage. This will not be true for all other file system drivers; e.g. the FAT filesystem stores short filenames in the OEM codepage, so some files on FAT volumes remain inaccessible through the ANSI APIs.
Similarly, $^X, @INC, and $ENV{PATH} are preprocessed at startup to make
sure all paths are valid in the ANSI codepage (if possible).
The WWiinn3322::::GGeettLLoonnggPPaatthhNNaammee(()) function now returns the UTF-8 encoded
correct long file name instead of using replacement characters to force
the name into the ANSI codepage. The new WWiinn3322::::GGeettAANNSSIIPPaatthhNNaammee(())
function can be used to turn a long pathname into a short one only if the
long one cannot be represented in the ANSI codepage.
Many other functions in the "Win32" module have been improved to accept
UTF-8 encoded arguments. Please see Win32 for details.
rreeaaddppiippee(()) iiss nnooww oovveerrrriiddaabbllee The built-in function rreeaaddppiippee(()) is now overridable. Overriding it permits also to override its operator counterpart, “qx//” (a.k.a. “``”). Moreover, it now defaults to $_ if no argument is provided. (Rafael Garcia-Suarez)
DDeeffaauulltt aarrgguummeenntt ffoorr rreeaaddlliinnee(()) rreeaaddlliinnee(()) now defaults to *ARGV if no argument is provided. (Rafael Garcia-Suarez)
ssttaattee(()) vvaarriiaabblleess A new class of variables has been introduced. State variables are similar to “my” variables, but are declared with the “state” keyword in place of “my”. They’re visible only in their lexical scope, but their value is persistent: unlike “my” variables, they’re not undefined at scope entry, but retain their previous value. (Rafael Garcia-Suarez, Nicholas Clark)
To use state variables, one needs to enable them by using
use feature 'state';
or by using the "-E" command-line switch in one-liners. See "Persistent
Private Variables" in perlsub.
SSttaacckkeedd ffiilleetteesstt ooppeerraattoorrss As a new form of syntactic sugar, it’s now possible to stack up filetest operators. You can now write “-f -w -x $file” in a row to mean “-x $file && -w _ && -f _”. See “-X” in perlfunc.
UUNNIIVVEERRSSAALL::::DDOOEESS(()) #
The "UNIVERSAL" class has a new method, "DOES()". It has been added to
solve semantic problems with the "isa()" method. "isa()" checks for
inheritance, while "DOES()" has been designed to be overridden when
module authors use other types of relations between classes (in addition
to inheritance). (chromatic)
See "$obj->DOES( ROLE )" in UNIVERSAL.
FFoorrmmaattss Formats were improved in several ways. A new field, “^*”, can be used for variable-width, one-line-at-a-time text. Null characters are now handled correctly in picture lines. Using “@#” and “~~” together will now produce a compile-time error, as those format fields are incompatible. perlform has been improved, and miscellaneous bugs fixed.
BByyttee--oorrddeerr mmooddiiffiieerrss ffoorr ppaacckk(()) aanndd uunnppaacckk(()) There are two new byte-order modifiers, “>” (big-endian) and “<” (little- endian), that can be appended to most ppaacckk(()) and uunnppaacckk(()) template characters and groups to force a certain byte-order for that type or group. See “pack” in perlfunc and perlpacktut for details.
“"nnoo VVEERRSSIIOONN"” You can now use “no” followed by a version number to specify that you want to use a version of perl older than the specified one.
“"cchhddiirr"”,, “"cchhmmoodd"” aanndd “"cchhoowwnn"” oonn ffiilleehhaannddlleess “chdir”, “chmod” and “chown” can now work on filehandles as well as filenames, if the system supports respectively “fchdir”, “fchmod” and “fchown”, thanks to a patch provided by Gisle Aas.
OOSS ggrroouuppss $( and $) now return groups in the order where the OS returns them, thanks to Gisle Aas. This wasn’t previously the case.
RReeccuurrssiivvee ssoorrtt ssuubbss You can now use recursive subroutines with ssoorrtt(()), thanks to Robin Houston.
EExxcceeppttiioonnss iinn ccoonnssttaanntt ffoollddiinngg The constant folding routine is now wrapped in an exception handler, and if folding throws an exception (such as attempting to evaluate 0/0), perl now retains the current optree, rather than aborting the whole program. Without this change, programs would not compile if they had expressions that happened to generate exceptions, even though those expressions were in code that could never be reached at runtime. (Nicholas Clark, Dave Mitchell)
SSoouurrccee ffiilltteerrss iinn @@IINNCC It’s possible to enhance the mechanism of subroutine hooks in @INC by adding a source filter on top of the filehandle opened and returned by the hook. This feature was planned a long time ago, but wasn’t quite working until now. See “require” in perlfunc for details. (Nicholas Clark)
NNeeww iinntteerrnnaall vvaarriiaabblleess
“${^RE_DEBUG_FLAGS}” #
This variable controls what debug flags are in effect for the regular
expression engine when running under "use re "debug"". See re for
details.
“${^CHILD_ERROR_NATIVE}” #
This variable gives the native status returned by the last pipe
close, backtick command, successful call to wwaaiitt(()) or wwaaiittppiidd(()), or
from the ssyysstteemm(()) operator. See perlvar for details. (Contributed by
Gisle Aas.)
“${^RE_TRIE_MAXBUF}” #
See "Trie optimisation of literal string alternations".
“${^WIN32_SLOPPY_STAT}” #
See "Sloppy stat on Windows".
MMiisscceellllaanneeoouuss “unpack()” now defaults to unpacking the $_ variable.
"mkdir()" without arguments now defaults to $_.
The internal dump output has been improved, so that non-printable
characters such as newline and backspace are output in "\x" notation,
rather than octal.
The --CC option can no longer be used on the "#!" line. It wasn't working
there anyway, since the standard streams are already set up at this point
in the execution of the perl interpreter. You can use bbiinnmmooddee(()) instead
to get the desired behaviour.
UUCCDD 55..00..00 #
The copy of the Unicode Character Database included in Perl 5 has been
updated to version 5.0.0.
MMAADD #
MAD, which stands for _M_i_s_c_e_l_l_a_n_e_o_u_s _A_t_t_r_i_b_u_t_e _D_e_c_o_r_a_t_i_o_n, is a still-in-
development work leading to a Perl 5 to Perl 6 converter. To enable it,
it's necessary to pass the argument "-Dmad" to Configure. The obtained
perl isn't binary compatible with a regular perl 5.10, and has space and
speed penalties; moreover not all regression tests still pass with it.
(Larry Wall, Nicholas Clark)
kkiillll(()) oonn WWiinnddoowwss On Windows platforms, “kill(-9, $pid)” now kills a process tree. (On Unix, this delivers the signal to all processes in the same process group.)
IInnccoommppaattiibbllee CChhaannggeess PPaacckkiinngg aanndd UUTTFF--88 ssttrriinnggss The semantics of ppaacckk(()) and uunnppaacckk(()) regarding UTF-8-encoded data has been changed. Processing is now by default character per character instead of byte per byte on the underlying encoding. Notably, code that used things like “pack(“a*”, $string)” to see through the encoding of string will now simply get back the original $string. Packed strings can also get upgraded during processing when you store upgraded characters. You can get the old behaviour by using “use bytes”.
To be consistent with ppaacckk(()), the "C0" in uunnppaacckk(()) templates indicates
that the data is to be processed in character mode, i.e. character by
character; on the contrary, "U0" in uunnppaacckk(()) indicates UTF-8 mode, where
the packed string is processed in its UTF-8-encoded Unicode form on a
byte by byte basis. This is reversed with regard to perl 5.8.X, but now
consistent between ppaacckk(()) and uunnppaacckk(()).
Moreover, "C0" and "U0" can also be used in ppaacckk(()) templates to specify
respectively character and byte modes.
"C0" and "U0" in the middle of a pack or unpack format now switch to the
specified encoding mode, honoring parens grouping. Previously, parens
were ignored.
Also, there is a new ppaacckk(()) character format, "W", which is intended to
replace the old "C". "C" is kept for unsigned chars coded as bytes in the
strings internal representation. "W" represents unsigned (logical)
character values, which can be greater than 255. It is therefore more
robust when dealing with potentially UTF-8-encoded data (as "C" will wrap
values outside the range 0..255, and not respect the string encoding).
In practice, that means that pack formats are now encoding-neutral,
except "C".
For consistency, "A" in uunnppaacckk(()) format now trims all Unicode whitespace
from the end of the string. Before perl 5.9.2, it used to strip only the
classical ASCII space characters.
BByyttee//cchhaarraacctteerr ccoouunntt ffeeaattuurree iinn uunnppaacckk(()) A new uunnppaacckk(()) template character, “.”, returns the number of bytes or characters (depending on the selected encoding mode, see above) read so far.
TThhee $$ aanndd $$## vvaarriiaabblleess hhaavvee bbeeeenn rreemmoovveedd $*, which was deprecated in favor of the “/s” and “/m” regexp modifiers, has been removed.
The deprecated $# variable (output format for numbers) has been removed.
Two new severe warnings, "$#/$* is no longer supported", have been added.
ssuubbssttrr(()) llvvaalluueess aarree nnoo lloonnggeerr ffiixxeedd--lleennggtthh The lvalues returned by the three argument form of ssuubbssttrr(()) used to be a “fixed length window” on the original string. In some cases this could cause surprising action at distance or other undefined behaviour. Now the length of the window adjusts itself to the length of the string assigned to it.
PPaarrssiinngg ooff “”--ff “” The identifier “” is now forced to be a bareword after a filetest operator. This solves a number of misparsing issues when a global “” subroutine is defined.
“”::uunniiqquuee"” The “:unique” attribute has been made a no-op, since its current implementation was fundamentally flawed and not threadsafe.
EEffffeecctt ooff pprraaggmmaass iinn eevvaall The compile-time value of the “%^H” hint variable can now propagate into eval(”")uated code. This makes it more useful to implement lexical pragmas.
As a side-effect of this, the overloaded-ness of constants now propagates
into eval("").
cchhddiirr FFOOOO A bareword argument to cchhddiirr(()) is now recognized as a file handle. Earlier releases interpreted the bareword as a directory name. (Gisle Aas)
HHaannddlliinngg ooff ..ppmmcc ffiilleess An old feature of perl was that before “require” or “use” look for a file with a _._p_m extension, they will first look for a similar filename with a _._p_m_c extension. If this file is found, it will be loaded in place of any potentially existing file ending in a _._p_m extension.
Previously, _._p_m_c files were loaded only if more recent than the matching
_._p_m file. Starting with 5.9.4, they'll be always loaded if they exist.
$$^^VV iiss nnooww aa “"vveerrssiioonn"” oobbjjeecctt iinnsstteeaadd ooff aa vv--ssttrriinngg $^V can still be used with the %vd format in printf, but any character- level operations will now access the string representation of the “version” object and not the ordinals of a v-string. Expressions like “substr($^V, 0, 2)” or “split //, $^V” no longer work and must be rewritten.
@@-- aanndd @@++ iinn ppaatttteerrnnss The special arrays “@-” and “@+” are no longer interpolated in regular expressions. (Sadahiro Tomoyuki)
$$AAUUTTOOLLOOAADD ccaann nnooww bbee ttaaiinntteedd If you call a subroutine by a tainted name, and if it defers to an AUTOLOAD function, then $AUTOLOAD will be (correctly) tainted. (Rick Delaney)
TTaaiinnttiinngg aanndd pprriinnttff When perl is run under taint mode, “printf()” and “sprintf()” will now reject any tainted format argument. (Rafael Garcia-Suarez)
uunnddeeff aanndd ssiiggnnaall hhaannddlleerrss Undefining or deleting a signal handler via “undef $SIG{FOO}” is now equivalent to setting it to ‘DEFAULT’. (Rafael Garcia-Suarez)
ssttrriiccttuurreess aanndd ddeerreeffeerreenncciinngg iinn ddeeffiinneedd(()) “use strict ‘refs’” was ignoring taking a hard reference in an argument to ddeeffiinneedd(()), as in :
use strict 'refs';
my $x = 'foo';
if (defined $$x) {...}
This now correctly produces the run-time error "Can't use string as a
SCALAR ref while "strict refs" in use".
"defined @$foo" and "defined %$bar" are now also subject to "strict
'refs'" (that is, $foo and $bar shall be proper references there.)
("defined(@foo)" and "defined(%bar)" are discouraged constructs anyway.)
(Nicholas Clark)
“”((??pp{{}}))“” hhaass bbeeeenn rreemmoovveedd The regular expression construct “(?p{})”, which was deprecated in perl 5.8, has been removed. Use “(??{})” instead. (Rafael Garcia-Suarez)
PPsseeuuddoo--hhaasshheess hhaavvee bbeeeenn rreemmoovveedd Support for pseudo-hashes has been removed from Perl 5.9. (The “fields” pragma remains here, but uses an alternate implementation.)
RReemmoovvaall ooff tthhee bbyytteeccooddee ccoommppiilleerr aanndd ooff ppeerrllcccc “perlcc”, the byteloader and the supporting modules (B::C, B::CC, B::Bytecode, etc.) are no longer distributed with the perl sources. Those experimental tools have never worked reliably, and, due to the lack of volunteers to keep them in line with the perl interpreter developments, it was decided to remove them instead of shipping a broken version of those. The last version of those modules can be found with perl 5.9.4.
However the B compiler framework stays supported in the perl core, as
with the more useful modules it has permitted (among others, B::Deparse
and B::Concise).
RReemmoovvaall ooff tthhee JJPPLL The JPL (Java-Perl Lingo) has been removed from the perl sources tarball.
RReeccuurrssiivvee iinnhheerriittaannccee ddeetteecctteedd eeaarrlliieerr Perl will now immediately throw an exception if you modify any package’s @ISA in such a way that it would cause recursive inheritance.
Previously, the exception would not occur until Perl attempted to make
use of the recursive inheritance while resolving a method or doing a
"$foo->isa($bar)" lookup.
wwaarrnniinnggss::::eennaabblleedd aanndd wwaarrnniinnggss::::wwaarrnniiff cchhaannggeedd ttoo ffaavvoorr uusseerrss ooff mmoodduulleess The behaviour in 5.10.x favors the person using the module; The behaviour in 5.8.x favors the module writer;
Assume the following code:
main calls Foo::Bar::baz()
Foo::Bar inherits from Foo::Base
Foo::Bar::baz() calls Foo::Base::_bazbaz()
Foo::Base::_bazbaz() calls: warnings::warnif('substr', 'some warning
message');
On 5.8.x, the code warns when Foo::Bar contains "use warnings;" It does
not matter if Foo::Base or main have warnings enabled to disable the
warning one has to modify Foo::Bar.
On 5.10.0 and newer, the code warns when main contains "use warnings;" It
does not matter if Foo::Base or Foo::Bar have warnings enabled to disable
the warning one has to modify main.
MMoodduulleess aanndd PPrraaggmmaattaa UUppggrraaddiinngg iinnddiivviidduuaall ccoorree mmoodduulleess Even more core modules are now also available separately through the CPAN. If you wish to update one of these modules, you don’t need to wait for a new perl release. From within the cpan shell, running the ‘r’ command will report on modules with upgrades available. See “perldoc CPAN” for more information.
PPrraaggmmaattaa CChhaannggeess “feature” The new pragma “feature” is used to enable new features that might break old code. See “The “feature” pragma” above.
"mro"
This new pragma enables to change the algorithm used to resolve
inherited methods. See "New Pragma, "mro"" above.
Scoping of the "sort" pragma
The "sort" pragma is now lexically scoped. Its effect used to be
global.
Scoping of "bignum", "bigint", "bigrat"
The three numeric pragmas "bignum", "bigint" and "bigrat" are now
lexically scoped. (Tels)
"base"
The "base" pragma now warns if a class tries to inherit from itself.
(Curtis "Ovid" Poe)
"strict" and "warnings"
"strict" and "warnings" will now complain loudly if they are loaded
via incorrect casing (as in "use Strict;"). (Johan Vromans)
"version"
The "version" module provides support for version objects.
"warnings"
The "warnings" pragma doesn't load "Carp" anymore. That means that
code that used "Carp" routines without having loaded it at compile
time might need to be adjusted; typically, the following (faulty)
code won't work anymore, and will require parentheses to be added
after the function name:
use warnings;
require Carp;
Carp::confess 'argh';
"less"
"less" now does something useful (or at least it tries to). In fact,
it has been turned into a lexical pragma. So, in your modules, you
can now test whether your users have requested to use less CPU, or
less memory, less magic, or maybe even less fat. See less for more.
(Joshua ben Jore)
NNeeww mmoodduulleess • “encoding::warnings”, by Audrey Tang, is a module to emit warnings whenever an ASCII character string containing high-bit bytes is implicitly converted into UTF-8. It’s a lexical pragma since Perl 5.9.4; on older perls, its effect is global.
• "Module::CoreList", by Richard Clamp, is a small handy module that
tells you what versions of core modules ship with any versions of
Perl 5. It comes with a command-line frontend, "corelist".
• "Math::BigInt::FastCalc" is an XS-enabled, and thus faster, version
of "Math::BigInt::Calc".
• "Compress::Zlib" is an interface to the zlib compression library. It
comes with a bundled version of zlib, so having a working zlib is not
a prerequisite to install it. It's used by "Archive::Tar" (see
below).
• "IO::Zlib" is an "IO::"-style interface to "Compress::Zlib".
• "Archive::Tar" is a module to manipulate "tar" archives.
• "Digest::SHA" is a module used to calculate many types of SHA
digests, has been included for SHA support in the CPAN module.
• "ExtUtils::CBuilder" and "ExtUtils::ParseXS" have been added.
• "Hash::Util::FieldHash", by Anno Siegel, has been added. This module
provides support for _f_i_e_l_d _h_a_s_h_e_s: hashes that maintain an
association of a reference with a value, in a thread-safe garbage-
collected way. Such hashes are useful to implement inside-out
objects.
• "Module::Build", by Ken Williams, has been added. It's an alternative
to "ExtUtils::MakeMaker" to build and install perl modules.
• "Module::Load", by Jos Boumans, has been added. It provides a single
interface to load Perl modules and _._p_l files.
• "Module::Loaded", by Jos Boumans, has been added. It's used to mark
modules as loaded or unloaded.
• "Package::Constants", by Jos Boumans, has been added. It's a simple
helper to list all constants declared in a given package.
• "Win32API::File", by Tye McQueen, has been added (for Windows
builds). This module provides low-level access to Win32 system API
calls for files/dirs.
• "Locale::Maketext::Simple", needed by CPANPLUS, is a simple wrapper
around "Locale::Maketext::Lexicon". Note that
"Locale::Maketext::Lexicon" isn't included in the perl core; the
behaviour of "Locale::Maketext::Simple" gracefully degrades when the
later isn't present.
• "Params::Check" implements a generic input parsing/checking
mechanism. It is used by CPANPLUS.
• "Term::UI" simplifies the task to ask questions at a terminal prompt.
• "Object::Accessor" provides an interface to create per-object
accessors.
• "Module::Pluggable" is a simple framework to create modules that
accept pluggable sub-modules.
• "Module::Load::Conditional" provides simple ways to query and
possibly load installed modules.
• "Time::Piece" provides an object oriented interface to time
functions, overriding the built-ins llooccaallttiimmee(()) and ggmmttiimmee(()).
• "IPC::Cmd" helps to find and run external commands, possibly
interactively.
• "File::Fetch" provide a simple generic file fetching mechanism.
• "Log::Message" and "Log::Message::Simple" are used by the log
facility of "CPANPLUS".
• "Archive::Extract" is a generic archive extraction mechanism for _._t_a_r
(plain, gzipped or bzipped) or _._z_i_p files.
• "CPANPLUS" provides an API and a command-line tool to access the CPAN
mirrors.
• "Pod::Escapes" provides utilities that are useful in decoding Pod
E<...> sequences.
• "Pod::Simple" is now the backend for several of the Pod-related
modules included with Perl.
SSeelleecctteedd CChhaannggeess ttoo CCoorree MMoodduulleess “Attribute::Handlers” “Attribute::Handlers” can now report the caller’s file and line number. (David Feldman)
All interpreted attributes are now passed as array references.
(Damian Conway)
"B::Lint"
"B::Lint" is now based on "Module::Pluggable", and so can be extended
with plugins. (Joshua ben Jore)
"B" It's now possible to access the lexical pragma hints ("%^H") by using
the method BB::::CCOOPP::::hhiinnttss__hhaasshh(()). It returns a "B::RHE" object, which
in turn can be used to get a hash reference via the method
BB::::RRHHEE::::HHAASSHH(()). (Joshua ben Jore)
"Thread"
As the old 5005thread threading model has been removed, in favor of
the ithreads scheme, the "Thread" module is now a compatibility
wrapper, to be used in old code only. It has been removed from the
default list of dynamic extensions.
UUttiilliittyy CChhaannggeess perl -d The Perl debugger can now save all debugger commands for sourcing later; notably, it can now emulate stepping backwards, by restarting and rerunning all bar the last command from a saved command history.
It can also display the parent inheritance tree of a given class,
with the "i" command.
ptar
"ptar" is a pure perl implementation of "tar" that comes with
"Archive::Tar".
ptardiff
"ptardiff" is a small utility used to generate a diff between the
contents of a tar archive and a directory tree. Like "ptar", it comes
with "Archive::Tar".
shasum
"shasum" is a command-line utility, used to print or to check SHA
digests. It comes with the new "Digest::SHA" module.
corelist
The "corelist" utility is now installed with perl (see "New modules"
above).
h2ph and h2xs
"h2ph" and "h2xs" have been made more robust with regard to "modern"
C code.
"h2xs" implements a new option "--use-xsloader" to force use of
"XSLoader" even in backwards compatible modules.
The handling of authors' names that had apostrophes has been fixed.
Any enums with negative values are now skipped.
perlivp
"perlivp" no longer checks for _*_._p_h files by default. Use the new
"-a" option to run _a_l_l tests.
find2perl
"find2perl" now assumes "-print" as a default action. Previously, it
needed to be specified explicitly.
Several bugs have been fixed in "find2perl", regarding "-exec" and
"-eval". Also the options "-path", "-ipath" and "-iname" have been
added.
config_data
"config_data" is a new utility that comes with "Module::Build". It
provides a command-line interface to the configuration of Perl
modules that use Module::Build's framework of configurability (that
is, *::ConfigData modules that contain local configuration
information for their parent modules.)
cpanp
"cpanp", the CPANPLUS shell, has been added. ("cpanp-run-perl", a
helper for CPANPLUS operation, has been added too, but isn't intended
for direct use).
cpan2dist
"cpan2dist" is a new utility that comes with CPANPLUS. It's a tool to
create distributions (or packages) from CPAN modules.
pod2html
The output of "pod2html" has been enhanced to be more customizable
via CSS. Some formatting problems were also corrected. (Jari Aalto)
NNeeww DDooccuummeennttaattiioonn The perlpragma manpage documents how to write one’s own lexical pragmas in pure Perl (something that is possible starting with 5.9.4).
The new perlglossary manpage is a glossary of terms used in the Perl
documentation, technical and otherwise, kindly provided by O'Reilly
Media, Inc.
The perlreguts manpage, courtesy of Yves Orton, describes internals of
the Perl regular expression engine.
The perlreapi manpage describes the interface to the perl interpreter
used to write pluggable regular expression engines (by Ævar Arnfjörð
Bjarmason).
The perlunitut manpage is a tutorial for programming with Unicode and
string encodings in Perl, courtesy of Juerd Waalboer.
A new manual page, perlunifaq (the Perl Unicode FAQ), has been added
(Juerd Waalboer).
The perlcommunity manpage gives a description of the Perl community on
the Internet and in real life. (Edgar "Trizor" Bering)
The CORE manual page documents the "CORE::" namespace. (Tels)
The long-existing feature of "/(?{...})/" regexps setting $_ and ppooss(()) is
now documented.
PPeerrffoorrmmaannccee EEnnhhaanncceemmeennttss IInn--ppllaaccee ssoorrttiinngg Sorting arrays in place ("@a = sort @a") is now optimized to avoid making a temporary copy of the array.
Likewise, "reverse sort ..." is now optimized to sort in reverse,
avoiding the generation of a temporary intermediate list.
LLeexxiiccaall aarrrraayy aacccceessss Access to elements of lexical arrays via a numeric constant between 0 and 255 is now faster. (This used to be only the case for global arrays.)
XXSS--aassssiisstteedd SSWWAASSHHGGEETT Some pure-perl code that perl was using to retrieve Unicode properties and transliteration mappings has been reimplemented in XS.
CCoonnssttaanntt ssuubbrroouuttiinneess The interpreter internals now support a far more memory efficient form of inlineable constants. Storing a reference to a constant value in a symbol table is equivalent to a full typeglob referencing a constant subroutine, but using about 400 bytes less memory. This proxy constant subroutine is automatically upgraded to a real typeglob with subroutine if necessary. The approach taken is analogous to the existing space optimisation for subroutine stub declarations, which are stored as plain scalars in place of the full typeglob.
Several of the core modules have been converted to use this feature for
their system dependent constants - as a result "use POSIX;" now takes
about 200K less memory.
“"PPEERRLL__DDOONNTT__CCRREEAATTEE__GGVVSSVV"” #
The new compilation flag "PERL_DONT_CREATE_GVSV", introduced as an option
in perl 5.8.8, is turned on by default in perl 5.9.3. It prevents perl
from creating an empty scalar with every new typeglob. See perl589delta
for details.
WWeeaakk rreeffeerreenncceess aarree cchheeaappeerr Weak reference creation is now _O_(_1_) rather than _O_(_n_), courtesy of Nicholas Clark. Weak reference deletion remains _O_(_n_), but if deletion only happens at program exit, it may be skipped completely.
ssoorrtt(()) eennhhaanncceemmeennttss Salvador Fandiño provided improvements to reduce the memory usage of “sort” and to speed up some cases.
MMeemmoorryy ooppttiimmiissaattiioonnss Several internal data structures (typeglobs, GVs, CVs, formats) have been restructured to use less memory. (Nicholas Clark)
UUTTFF--88 ccaacchhee ooppttiimmiissaattiioonn The UTF-8 caching code is now more efficient, and used more often. (Nicholas Clark)
SSllooppppyy ssttaatt oonn WWiinnddoowwss On Windows, perl’s ssttaatt(()) function normally opens the file to determine the link count and update attributes that may have been changed through hard links. Setting ${^WIN32_SLOPPY_STAT} to a true value speeds up ssttaatt(()) by not performing this operation. (Jan Dubois)
RReegguullaarr eexxpprreessssiioonnss ooppttiimmiissaattiioonnss Engine de-recursivised The regular expression engine is no longer recursive, meaning that patterns that used to overflow the stack will either die with useful explanations, or run to completion, which, since they were able to blow the stack before, will likely take a very long time to happen. If you were experiencing the occasional stack overflow (or segfault) and upgrade to discover that now perl apparently hangs instead, look for a degenerate regex. (Dave Mitchell)
Single char char-classes treated as literals
Classes of a single character are now treated the same as if the
character had been used as a literal, meaning that code that uses
char-classes as an escaping mechanism will see a speedup. (Yves
Orton)
Trie optimisation of literal string alternations
Alternations, where possible, are optimised into more efficient
matching structures. String literal alternations are merged into a
trie and are matched simultaneously. This means that instead of O(N)
time for matching N alternations at a given point, the new code
performs in O(1) time. A new special variable, ${^RE_TRIE_MAXBUF},
has been added to fine-tune this optimization. (Yves Orton)
NNoottee:: Much code exists that works around perl's historic poor
performance on alternations. Often the tricks used to do so will
disable the new optimisations. Hopefully the utility modules used for
this purpose will be educated about these new optimisations.
Aho-Corasick start-point optimisation
When a pattern starts with a trie-able alternation and there aren't
better optimisations available, the regex engine will use Aho-
Corasick matching to find the start point. (Yves Orton)
IInnssttaallllaattiioonn aanndd CCoonnffiigguurraattiioonn IImmpprroovveemmeennttss CCoonnffiigguurraattiioonn iimmpprroovveemmeennttss “-Dusesitecustomize” Run-time customization of @INC can be enabled by passing the “-Dusesitecustomize” flag to Configure. When enabled, this will make perl run _$_s_i_t_e_l_i_b_e_x_p_/_s_i_t_e_c_u_s_t_o_m_i_z_e_._p_l before anything else. This script can then be set up to add additional entries to @INC.
Relocatable installations
There is now Configure support for creating a relocatable perl tree.
If you Configure with "-Duserelocatableinc", then the paths in @INC
(and everything else in %Config) can be optionally located via the
path of the perl executable.
That means that, if the string ".../" is found at the start of any
path, it's substituted with the directory of $^X. So, the relocation
can be configured on a per-directory basis, although the default with
"-Duserelocatableinc" is that everything is relocated. The initial
install is done to the original configured prefix.
ssttrrllccaatt(()) and ssttrrllccppyy(())
The configuration process now detects whether ssttrrllccaatt(()) and ssttrrllccppyy(())
are available. When they are not available, perl's own version is
used (from Russ Allbery's public domain implementation). Various
places in the perl interpreter now use them. (Steve Peters)
"d_pseudofork" and "d_printf_format_null"
A new configuration variable, available as $Config{d_pseudofork} in
the Config module, has been added, to distinguish real ffoorrkk(()) support
from fake pseudofork used on Windows platforms.
A new configuration variable, "d_printf_format_null", has been added,
to see if printf-like formats are allowed to be NULL.
Configure help
"Configure -h" has been extended with the most commonly used options.
CCoommppiillaattiioonn iimmpprroovveemmeennttss Parallel build Parallel makes should work properly now, although there may still be problems if “make test” is instructed to run in parallel.
Borland's compilers support
Building with Borland's compilers on Win32 should work more smoothly.
In particular Steve Hay has worked to side step many warnings emitted
by their compilers and at least one C compiler internal error.
Static build on Windows
Perl extensions on Windows now can be statically built into the Perl
DLL. #
Also, it's now possible to build a "perl-static.exe" that doesn't
depend on the Perl DLL on Win32. See the Win32 makefiles for details.
(Vadim Konovalov)
ppport.h files
All _p_p_p_o_r_t_._h files in the XS modules bundled with perl are now
autogenerated at build time. (Marcus Holland-Moritz)
C++ compatibility
Efforts have been made to make perl and the core XS modules
compilable with various C++ compilers (although the situation is not
perfect with some of the compilers on some of the platforms tested.)
Support for Microsoft 64-bit compiler
Support for building perl with Microsoft's 64-bit compiler has been
improved. (ActiveState)
Visual C++
Perl can now be compiled with Microsoft Visual C++ 2005 (and 2008
Beta 2).
Win32 builds
All win32 builds (MS-Win, WinCE) have been merged and cleaned up.
IInnssttaallllaattiioonn iimmpprroovveemmeennttss Module auxiliary files README files and changelogs for CPAN modules bundled with perl are no longer installed.
NNeeww OOrr IImmpprroovveedd PPllaattffoorrmmss Perl has been reported to work on Symbian OS. See perlsymbian for more information.
Many improvements have been made towards making Perl work correctly on
z/OS.
Perl has been reported to work on DragonFlyBSD and MidnightBSD.
Perl has also been reported to work on NexentaOS (
http://www.gnusolaris.org/ ).
The VMS port has been improved. See perlvms.
Support for Cray XT4 Catamount/Qk has been added. See _h_i_n_t_s_/_c_a_t_a_m_o_u_n_t_._s_h
in the source code distribution for more information.
Vendor patches have been merged for RedHat and Gentoo.
DDyynnaaLLooaaddeerr::::ddll__uunnllooaadd__ffiillee(()) now works on Windows.
SSeelleecctteedd BBuugg FFiixxeess strictures in regexp-eval blocks “strict” wasn’t in effect in regexp-eval blocks ("/(?{…})/").
Calling CCOORREE::::rreeqquuiirree(())
CCOORREE::::rreeqquuiirree(()) and CCOORREE::::ddoo(()) were always parsed as rreeqquuiirree(()) and
ddoo(()) when they were overridden. This is now fixed.
Subscripts of slices
You can now use a non-arrowed form for chained subscripts after a
list slice, like in:
({foo => "bar"})[0]{foo}
This used to be a syntax error; a "->" was required.
"no warnings 'category'" works correctly with -w
Previously when running with warnings enabled globally via "-w",
selective disabling of specific warning categories would actually
turn off all warnings. This is now fixed; now "no warnings 'io';"
will only turn off warnings in the "io" class. Previously it would
erroneously turn off all warnings.
threads improvements
Several memory leaks in ithreads were closed. Also, ithreads were
made less memory-intensive.
"threads" is now a dual-life module, also available on CPAN. It has
been expanded in many ways. A kkiillll(()) method is available for thread
signalling. One can get thread status, or the list of running or
joinable threads.
A new "threads->exit()" method is used to exit from the application
(this is the default for the main thread) or from the current thread
only (this is the default for all other threads). On the other hand,
the eexxiitt(()) built-in now always causes the whole application to
terminate. (Jerry D. Hedden)
cchhrr(()) and negative values
cchhrr(()) on a negative value now gives "\x{FFFD}", the Unicode
replacement character, unless when the "bytes" pragma is in effect,
where the low eight bits of the value are used.
PERL5SHELL and tainting
On Windows, the PERL5SHELL environment variable is now checked for
taintedness. (Rafael Garcia-Suarez)
Using *FILE{IO}
"stat()" and "-X" filetests now treat *FILE{IO} filehandles like
*FILE filehandles. (Steve Peters)
Overloading and reblessing
Overloading now works when references are reblessed into another
class. Internally, this has been implemented by moving the flag for
"overloading" from the reference to the referent, which logically is
where it should always have been. (Nicholas Clark)
Overloading and UTF-8
A few bugs related to UTF-8 handling with objects that have
stringification overloaded have been fixed. (Nicholas Clark)
eval memory leaks fixed
Traditionally, "eval 'syntax error'" has leaked badly. Many (but not
all) of these leaks have now been eliminated or reduced. (Dave
Mitchell)
Random device on Windows
In previous versions, perl would read the file _/_d_e_v_/_u_r_a_n_d_o_m if it
existed when seeding its random number generator. That file is
unlikely to exist on Windows, and if it did would probably not
contain appropriate data, so perl no longer tries to read it on
Windows. (Alex Davies)
PERLIO_DEBUG #
The "PERLIO_DEBUG" environment variable no longer has any effect for
setuid scripts and for scripts run with --TT.
Moreover, with a thread-enabled perl, using "PERLIO_DEBUG" could lead
to an internal buffer overflow. This has been fixed.
PerlIO::scalar and read-only scalars
PerlIO::scalar will now prevent writing to read-only scalars.
Moreover, sseeeekk(()) is now supported with PerlIO::scalar-based
filehandles, the underlying string being zero-filled as needed.
(Rafael, Jarkko Hietaniemi)
ssttuuddyy(()) and UTF-8
ssttuuddyy(()) never worked for UTF-8 strings, but could lead to false
results. It's now a no-op on UTF-8 data. (Yves Orton)
Critical signals
The signals SIGILL, SIGBUS and SIGSEGV are now always delivered in an
"unsafe" manner (contrary to other signals, that are deferred until
the perl interpreter reaches a reasonably stable state; see "Deferred
Signals (Safe Signals)" in perlipc). (Rafael)
@INC-hook fix
When a module or a file is loaded through an @INC-hook, and when this
hook has set a filename entry in %INC, __FILE__ is now set for this
module accordingly to the contents of that %INC entry. (Rafael)
"-t" switch fix
The "-w" and "-t" switches can now be used together without messing
up which categories of warnings are activated. (Rafael)
Duping UTF-8 filehandles
Duping a filehandle which has the ":utf8" PerlIO layer set will now
properly carry that layer on the duped filehandle. (Rafael)
Localisation of hash elements
Localizing a hash element whose key was given as a variable didn't
work correctly if the variable was changed while the llooccaall(()) was in
effect (as in "local $h{$x}; ++$x"). (Bo Lindbergh)
NNeeww oorr CChhaannggeedd DDiiaaggnnoossttiiccss Use of uninitialized value Perl will now try to tell you the name of the variable (if any) that was undefined.
Deprecated use of mmyy(()) in false conditional
A new deprecation warning, _D_e_p_r_e_c_a_t_e_d _u_s_e _o_f _mm_yy_((_)) _i_n _f_a_l_s_e
_c_o_n_d_i_t_i_o_n_a_l, has been added, to warn against the use of the dubious
and deprecated construct
my $x if 0;
See perldiag. Use "state" variables instead.
!=~ should be !~
A new warning, "!=~ should be !~", is emitted to prevent this
misspelling of the non-matching operator.
Newline in left-justified string
The warning _N_e_w_l_i_n_e _i_n _l_e_f_t_-_j_u_s_t_i_f_i_e_d _s_t_r_i_n_g has been removed.
Too late for "-T" option
The error _T_o_o _l_a_t_e _f_o_r _"_-_T_" _o_p_t_i_o_n has been reformulated to be more
descriptive.
"%s" variable %s masks earlier declaration
This warning is now emitted in more consistent cases; in short, when
one of the declarations involved is a "my" variable:
my $x; my $x; # warns
my $x; our $x; # warns
our $x; my $x; # warns
On the other hand, the following:
our $x; our $x;
now gives a ""our" variable %s redeclared" warning.
rreeaaddddiirr(())/cclloosseeddiirr(())/etc. attempted on invalid dirhandle
These new warnings are now emitted when a dirhandle is used but is
either closed or not really a dirhandle.
Opening dirhandle/filehandle %s also as a file/directory
Two deprecation warnings have been added: (Rafael)
Opening dirhandle %s also as a file
Opening filehandle %s also as a directory
Use of -P is deprecated
Perl's command-line switch "-P" is now deprecated.
v-string in use/require is non-portable
Perl will warn you against potential backwards compatibility problems
with the "use VERSION" syntax.
perl -V
"perl -V" has several improvements, making it more useable from shell
scripts to get the value of configuration variables. See perlrun for
details.
CChhaannggeedd IInntteerrnnaallss In general, the source code of perl has been refactored, tidied up, and optimized in many places. Also, memory management and allocation has been improved in several points.
When compiling the perl core with gcc, as many gcc warning flags are
turned on as is possible on the platform. (This quest for cleanliness
doesn't extend to XS code because we cannot guarantee the tidiness of
code we didn't write.) Similar strictness flags have been added or
tightened for various other C compilers.
RReeoorrddeerriinngg ooff SSVVtt__ ccoonnssttaannttss The relative ordering of constants that define the various types of “SV” have changed; in particular, “SVt_PVGV” has been moved before “SVt_PVLV”, “SVt_PVAV”, “SVt_PVHV” and “SVt_PVCV”. This is unlikely to make any difference unless you have code that explicitly makes assumptions about that ordering. (The inheritance hierarchy of “B::*” objects has been changed to reflect this.)
EElliimmiinnaattiioonn ooff SSVVtt__PPVVBBMM Related to this, the internal type “SVt_PVBM” has been removed. This dedicated type of “SV” was used by the “index” operator and parts of the regexp engine to facilitate fast Boyer-Moore matches. Its use internally has been replaced by “SV"s of type “SVt_PVGV”.
NNeeww ttyyppee SSVVtt__BBIINNDD A new type “SVt_BIND” has been added, in readiness for the project to implement Perl 6 on 5. There deliberately is no implementation yet, and they cannot yet be created or destroyed.
RReemmoovvaall ooff CCPPPP ssyymmbboollss The C preprocessor symbols “PERL_PM_APIVERSION” and “PERL_XS_APIVERSION”, which were supposed to give the version number of the oldest perl binary- compatible (resp. source-compatible) with the present one, were not used, and sometimes had misleading values. They have been removed.
LLeessss ssppaaccee iiss uusseedd bbyy ooppss The “BASEOP” structure now uses less space. The “op_seq” field has been removed and replaced by a single bit bit-field “op_opt”. “op_type” is now 9 bits long. (Consequently, the “B::OP” class doesn’t provide an “seq” method anymore.)
NNeeww ppaarrsseerr perl’s parser is now generated by bison (it used to be generated by byacc.) As a result, it seems to be a bit more robust.
Also, Dave Mitchell improved the lexer debugging output under "-DT".
UUssee ooff “"ccoonnsstt"” Andy Lester supplied many improvements to determine which function parameters and local variables could actually be declared “const” to the C compiler. Steve Peters provided new *_set macros and reworked the core to use these rather than assigning to macros in LVALUE context.
MMaatthhoommss A new file, _m_a_t_h_o_m_s_._c, has been added. It contains functions that are no longer used in the perl core, but that remain available for binary or source compatibility reasons. However, those functions will not be compiled in if you add “-DNO_MATHOMS” in the compiler flags.
“"AAvvFFLLAAGGSS"” hhaass bbeeeenn rreemmoovveedd The “AvFLAGS” macro has been removed.
“"aavv__“” cchhaannggeess The “av_()” functions, used to manipulate arrays, no longer accept null “AV” parameters.
$$^^HH aanndd %%^^HH The implementation of the special variables $^H and %^H has changed, to allow implementing lexical pragmas in pure Perl.
BB:::: mmoodduulleess iinnhheerriittaannccee cchhaannggeedd The inheritance hierarchy of “B::” modules has changed; “B::NV” now inherits from “B::SV” (it used to inherit from “B::IV”).
AAnnoonnyymmoouuss hhaasshh aanndd aarrrraayy ccoonnssttrruuccttoorrss The anonymous hash and array constructors now take 1 op in the optree instead of 3, now that pp_anonhash and pp_anonlist return a reference to a hash/array when the op is flagged with OPf_SPECIAL. (Nicholas Clark)
KKnnoowwnn PPrroobblleemmss There’s still a remaining problem in the implementation of the lexical $_: it doesn’t work inside “/(?{…})/” blocks. (See the TODO test in _t_/_o_p_/_m_y_d_e_f_._t.)
Stacked filetest operators won't work when the "filetest" pragma is in
effect, because they rely on the ssttaatt(()) buffer "_" being populated, and
filetest bypasses ssttaatt(()).
UUTTFF--88 pprroobblleemmss The handling of Unicode still is unclean in several places, where it’s dependent on whether a string is internally flagged as UTF-8. This will be made more consistent in perl 5.12, but that won’t be possible without a certain amount of backwards incompatibility.
PPllaattffoorrmm SSppeecciiffiicc PPrroobblleemmss When compiled with g++ and thread support on Linux, it’s reported that the $! stops working correctly. This is related to the fact that the glibc provides two ssttrreerrrroorr__rr(3) implementation, and perl selects the wrong one.
RReeppoorrttiinngg BBuuggss If you find what you think is a bug, you might check the articles recently posted to the comp.lang.perl.misc newsgroup and the perl bug database at http://rt.perl.org/rt3/ . There may also be information at http://www.perl.org/ , the Perl Home Page.
If you believe you have an unreported bug, please run the ppeerrllbbuugg program
included with your release. Be sure to trim your bug down to a tiny but
sufficient test case. Your bug report, along with the output of "perl
-V", will be sent off to perlbug@perl.org to be analysed by the Perl
porting team.
SSEEEE AALLSSOO #
The _C_h_a_n_g_e_s file and the perl590delta to perl595delta man pages for
exhaustive details on what changed.
The _I_N_S_T_A_L_L file for how to build Perl.
The _R_E_A_D_M_E file for general stuff.
The _A_r_t_i_s_t_i_c and _C_o_p_y_i_n_g files for copyright information.
perl v5.36.3 2023-02-15 PERL5100DELTA(1)