perldelta.pod

ARM上的如果你对底层感兴趣

=item CPAN

See <perlmodinstall> and L<CPAN>.

=item Cwd

Cwd::cwd is faster on most platforms.

=item Benchmark

Keeps better time.

=back

=head1 Utility Changes

C<h2ph> and related utilities have been vastly overhauled.

C<perlcc>, a new experimental front end for the compiler is available.

The crude GNU C<configure> emulator is now called C<configure.gnu> to
avoid trampling on C<Configure> under case-insensitive filesystems.

C<perldoc> used to be rather slow.  The slower features are now optional.
In particular, case-insensitive searches need the C<-i> switch, and
recursive searches need C<-r>.  You can set these switches in the
C<PERLDOC> environment variable to get the old behavior.

=head1 Documentation Changes

Config.pm now has a glossary of variables.

F<Porting/patching.pod> has detailed instructions on how to create and
submit patches for perl.

L<perlport> specifies guidelines on how to write portably. 

L<perlmodinstall> describes how to fetch and install modules from C<CPAN>
sites.

Some more Perl traps are documented now.  See L<perltrap>.

=head1 New Diagnostics

=over

=item Ambiguous call resolved as CORE::%s(), qualify as such or use &

(W) A subroutine you have declared has the same name as a Perl keyword,
and you have used the name without qualification for calling one or the
other.  Perl decided to call the builtin because the subroutine is
not imported.

To force interpretation as a subroutine call, either put an ampersand
before the subroutine name, or qualify the name with its package.
Alternatively, you can import the subroutine (or pretend that it's
imported with the C<use subs> pragma).

To silently interpret it as the Perl operator, use the C<CORE::> prefix
on the operator (e.g. C<CORE::log($x)>) or by declaring the subroutine
to be an object method (see L<attrs>).

=item Bad index while coercing array into hash

(F) The index looked up in the hash found as the 0'th element of a
pseudo-hash is not legal.  Index values must be at 1 or greater.
See L<perlref>.

=item Bareword "%s" refers to nonexistent package

(W) You used a qualified bareword of the form C<Foo::>, but
the compiler saw no other uses of that namespace before that point.
Perhaps you need to predeclare a package?

=item Can't call method "%s" on an undefined value

(F) You used the syntax of a method call, but the slot filled by the
object reference or package name contains an undefined value.
Something like this will reproduce the error:

    $BADREF = 42;
    process $BADREF 1,2,3;
    $BADREF->process(1,2,3);

=item Can't coerce array into hash

(F) You used an array where a hash was expected, but the array has no
information on how to map from keys to array indices.  You can do that
only with arrays that have a hash reference at index 0.

=item Can't goto subroutine from an eval-string

(F) The "goto subroutine" call can't be used to jump out of an eval "string".
(You can use it to jump out of an eval {BLOCK}, but you probably don't want to.)

=item Can't localize pseudo-hash element

(F) You said something like C<local $ar-E<gt>{'key'}>, where $ar is
a reference to a pseudo-hash.  That hasn't been implemented yet, but
you can get a similar effect by localizing the corresponding array
element directly -- C<local $ar-E<gt>[$ar-E<gt>[0]{'key'}]>.

=item Can't use %%! because Errno.pm is not available

(F) The first time the %! hash is used, perl automatically loads the
Errno.pm module. The Errno module is expected to tie the %! hash to
provide symbolic names for C<$!> errno values.

=item Cannot find an opnumber for "%s"

(F) A string of a form C<CORE::word> was given to prototype(), but
there is no builtin with the name C<word>.

=item Character class syntax [. .] is reserved for future extensions

(W) Within regular expression character classes ([]) the syntax beginning
with "[." and ending with ".]" is reserved for future extensions.
If you need to represent those character sequences inside a regular
expression character class, just quote the square brackets with the
backslash: "\[." and ".\]".

=item Character class syntax [: :] is reserved for future extensions

(W) Within regular expression character classes ([]) the syntax beginning
with "[:" and ending with ":]" is reserved for future extensions.
If you need to represent those character sequences inside a regular
expression character class, just quote the square brackets with the
backslash: "\[:" and ":\]".

=item Character class syntax [= =] is reserved for future extensions

(W) Within regular expression character classes ([]) the syntax
beginning with "[=" and ending with "=]" is reserved for future extensions.
If you need to represent those character sequences inside a regular
expression character class, just quote the square brackets with the
backslash: "\[=" and "=\]".

=item %s: Eval-group in insecure regular expression

(F) Perl detected tainted data when trying to compile a regular expression
that contains the C<(?{ ... })> zero-width assertion, which is unsafe.
See L<perlre/(?{ code })>, and L<perlsec>.

=item %s: Eval-group not allowed, use re 'eval'

(F) A regular expression contained the C<(?{ ... })> zero-width assertion,
but that construct is only allowed when the C<use re 'eval'> pragma is
in effect.  See L<perlre/(?{ code })>.

=item %s: Eval-group not allowed at run time

(F) Perl tried to compile a regular expression containing the C<(?{ ... })>
zero-width assertion at run time, as it would when the pattern contains
interpolated values.  Since that is a security risk, it is not allowed.
If you insist, you may still do this by explicitly building the pattern
from an interpolated string at run time and using that in an eval().
See L<perlre/(?{ code })>.

=item Explicit blessing to '' (assuming package main)

(W) You are blessing a reference to a zero length string.  This has
the effect of blessing the reference into the package main.  This is
usually not what you want.  Consider providing a default target
package, e.g. bless($ref, $p or 'MyPackage');

=item Illegal hex digit ignored

(W) You may have tried to use a character other than 0 - 9 or A - F in a
hexadecimal number.  Interpretation of the hexadecimal number stopped
before the illegal character.

=item No such array field

(F) You tried to access an array as a hash, but the field name used is
not defined.  The hash at index 0 should map all valid field names to
array indices for that to work.

=item No such field "%s" in variable %s of type %s

(F) You tried to access a field of a typed variable where the type
does not know about the field name.  The field names are looked up in
the %FIELDS hash in the type package at compile time.  The %FIELDS hash
is usually set up with the 'fields' pragma.

=item Out of memory during ridiculously large request

(F) You can't allocate more than 2^31+"small amount" bytes.  This error
is most likely to be caused by a typo in the Perl program. e.g., C<$arr[time]>
instead of C<$arr[$time]>.

=item Range iterator outside integer range

(F) One (or both) of the numeric arguments to the range operator ".."
are outside the range which can be represented by integers internally.
One possible workaround is to force Perl to use magical string
increment by prepending "0" to your numbers.

=item Recursive inheritance detected while looking for method '%s' in package '%s'

(F) More than 100 levels of inheritance were encountered while invoking a
method.  Probably indicates an unintended loop in your inheritance hierarchy.

=item Reference found where even-sized list expected

(W) You gave a single reference where Perl was expecting a list with
an even number of elements (for assignment to a hash). This
usually means that you used the anon hash constructor when you meant 
to use parens. In any case, a hash requires key/value B<pairs>.

    %hash = { one => 1, two => 2, };   # WRONG
    %hash = [ qw/ an anon array / ];   # WRONG
    %hash = ( one => 1, two => 2, );   # right
    %hash = qw( one 1 two 2 );                 # also fine

=item Undefined value assigned to typeglob

(W) An undefined value was assigned to a typeglob, a la C<*foo = undef>.
This does nothing.  It's possible that you really mean C<undef *foo>.

=item Use of reserved word "%s" is deprecated

(D) The indicated bareword is a reserved word.  Future versions of perl
may use it as a keyword, so you're better off either explicitly quoting
the word in a manner appropriate for its context of use, or using a
different name altogether.  The warning can be suppressed for subroutine
names by either adding a C<&> prefix, or using a package qualifier,
e.g. C<&our()>, or C<Foo::our()>.

=item perl: warning: Setting locale failed.

(S) The whole warning message will look something like:

       perl: warning: Setting locale failed.
       perl: warning: Please check that your locale settings:
               LC_ALL = "En_US",
               LANG = (unset)
           are supported and installed on your system.
       perl: warning: Falling back to the standard locale ("C").

Exactly what were the failed locale settings varies.  In the above the
settings were that the LC_ALL was "En_US" and the LANG had no value.
This error means that Perl detected that you and/or your system
administrator have set up the so-called variable system but Perl could
not use those settings.  This was not dead serious, fortunately: there
is a "default locale" called "C" that Perl can and will use, the
script will be run.  Before you really fix the problem, however, you
will get the same error message each time you run Perl.  How to really
fix the problem can be found in L<perllocale> section B<LOCALE PROBLEMS>.

=back


=head1 Obsolete Diagnostics

=over

=item Can't mktemp()

(F) The mktemp() routine failed for some reason while trying to process
a B<-e> switch.  Maybe your /tmp partition is full, or clobbered.

=item Can't write to temp file for B<-e>: %s

(F) The write routine failed for some reason while trying to process
a B<-e> switch.  Maybe your /tmp partition is full, or clobbered.

=item Cannot open temporary file

(F) The create routine failed for some reason while trying to process
a B<-e> switch.  Maybe your /tmp partition is full, or clobbered.

=back

=head1 BUGS

If you find what you think is a bug, you might check the headers of
recently posted articles in the comp.lang.perl.misc newsgroup.
There may also be information at http://www.perl.com/perl/, the Perl
Home Page.

If you believe you have an unreported bug, please run the 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 <F<[e-mail]>> to be
analysed by the Perl porting team.

=head1 SEE ALSO

The F<Changes> file for exhaustive details on what changed.

The F<INSTALL> file for how to build Perl.

The F<README> file for general stuff.

The F<Artistic> and F<Copying> files for copyright information.

=head1 HISTORY

Written by Gurusamy Sarathy <F<[e-mail]>>, with many contributions
from The Perl Porters.

Send omissions or corrections to <F<[e-mail]>>.

=cut