and is implemented using the new Opcode module. Please read the new
Opcode and Safe documentation.
+=head2 Fixed Parsing of $$<digit>, &$<digit>, etc.
+
+A bug in previous versions of Perl 5.0 prevented proper parsing of
+numeric special variables as symbolic references. That bug has been
+fixed. As a result, the string "$$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.
As a disincentive to casual use of this advanced feature,
there is no C<use English> long name for this variable.
-=item $^S
-
-The status returned by the last pipe close, back-tick (C<``>) command, or
-system() operator, in the native system format. On UNIX and UNIX-like
-systems, C<$^S> is a synonym for C<$?>. Elsewhere, C<$^S> can be used to
-determine aspects of child status that are system-specific. Check C<$^O>
-before using this variable. (Mnemonic: System-Specific Subprocess Status.
-Also known as $SYSTEM_CHILD_STATUS if you C<use English>.)
-
=back
=head2 New and Changed Built-in Functions
is now supported on more platforms, and prefers fcntl
to lockf when emulating.
+=item printf and sprintf
+
+now support "%i" as a synonym for "%d", and the "h" modifier.
+So "%hi" means "short integer in decimal", and "%ho" means
+"unsigned short integer as octal".
+
=item keys as an lvalue
As an lvalue, C<keys> allows you to increase the number of hash buckets
-allocated for the given associative array. This can gain you a measure
-of efficiency if you know the hash is going to get big. (This is
-similar to pre-extending an array by assigning a larger number to
-$#array.) If you say
+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;
You can now use my() (with or without the parentheses) in the control
expressions of control structures such as:
- while (my $line = <>) {
+ while (defined(my $line = <>)) {
$line = lc $line;
} continue {
print $line;
# implies:
A->VERSION(1.2);
-=item class()
-
-C<class> returns the class name of its object.
-
-=item is_instance()
-
-C<is_instance> returns true if its object is an instance of some
-class, false if its object is the class (package) itself. Example
-
- A->is_instance(); # False
-
- $var = 'A';
- $var->is_instance(); # False
-
- $ref = bless [], 'A';
- $ref->is_instance(); # True
-
-This can be useful for methods that wish to easily distinguish
-whether they were invoked as class or as instance methods.
-
- sub some_meth {
- my $classname = shift;
- if ($classname->is_instance()) {
- die "unexpectedly called as instance not class method";
- }
- .....
- }
-
=back
B<NOTE:> C<can> directly uses Perl's internal code for method lookup, and
=back
-=item Efficiency Enhancements
+=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.)
-All hash keys with the same string are only allocated once, so
-even if you have 100 copies of the same hash, the immutable keys
-never have to be re-allocated.
+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<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 C<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).
+
+=item -DTWO_POT_OPTIMIZE
+
+Similarly to C<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.
+
+=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<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 re-allocated.
+
=head1 Pragmata
-Three new pragmatic modules exist:
+Four new pragmatic modules exist:
=over
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<system> return genuine VMS status values instead of emulating POSIX;
+'exit', which makes C<exit> take a genuine VMS status value instead of
+assuming that C<exit 1> is an error; and 'time', which makes all times
+relative to the local time zone, in the VMS tradition.
+
=back
=head1 Modules
ExtUtils/Embed.pm Utilities for embedding Perl in C programs
ExtUtils/testlib.pm Fixes up @INC to use just-built extension
- Fatal.pm Make do-or-die equivalents of functions
FindBin.pm Find path of currently executing program
Class/Template.pm Structure/member template builder
error on the I<second> 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 so. The additions to the
+API allow passing keys as C<SV*>s, so that C<tied> hashes can be given
+real scalars as keys rather than plain strings (non-tied hashes still
+can only use strings as keys). New extensions must use the new hash
+access functions and macros if they wish to use C<SV*> keys. These
+additions also make it feasible to manipulate C<HE*>s (hash entries),
+which can be more efficient. See L<perlguts> for details.
+
=back
=head1 Documentation Changes
If you believe you have an unreported bug, please run the B<perlbug>
program included with your release. Make sure you trim your bug
down to a tiny but sufficient test case. Your bug report, along
-with the output of C<perl -V>, will be sent off to perlbug@perl.com
+with the output of C<perl -V>, will be sent off to F<perlbug@perl.com>
to be analysed by the Perl porting team.
=head1 SEE ALSO
projects / p5sagit/p5-mst-13.2.git / blobdiff