vice-versa. Compare with Win32::GetShortPathName and
Win32::GetLongPathName.
-This function has been added for Perl 5.006.
+This function has been added for Perl 5.6.
=item Win32::GetLastError()
absolute path. Compare with Win32::GetShortPathName and
Win32::GetFullPathName.
-This function has been added for Perl 5.006.
+This function has been added for Perl 5.6.
=item Win32::GetNextAvailDrive()
[CORE] Sets the value of the last error encountered to ERROR. This is
that value that will be returned by the Win32::GetLastError()
-function. This functions has been added for Perl 5.006.
+function. This functions has been added for Perl 5.6.
=item Win32::Sleep(TIME)
=head1 NAME
-perldelta - what's new for perl5.006 (as of 5.005_56)
+perldelta - what's new for perl v5.6 (as of v5.5.58)
=head1 DESCRIPTION
=item C<PERL_POLLUTE>
Release 5.005 grandfathered old global symbol names by providing preprocessor
-macros for extension source compatibility. As of release 5.006, these
+macros for extension source compatibility. As of release 5.6, these
preprocessor definitions are not available by default. You need to explicitly
compile perl with C<-DPERL_POLLUTE> to get these definitions. For
extensions still using the old symbols, this option can be
have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
EMBEDMYMALLOC preprocessor definitions.
-As of release 5.006, Perl's malloc family of functions have default names
+As of release 5.6, Perl's malloc family of functions have default names
distinct from the system versions. You need to explicitly compile perl with
C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
=item 23/May/99
-Extensive updates from the net in preparation for 5.006 release.
+Extensive updates from the net in preparation for 5.6 release.
=item 13/April/99
are a rag-tag band of highly altruistic individuals committed
to producing better software for free than you could hope to
purchase for money. You may snoop on pending developments via
-nntp://news.perl.com/perl.porters-gw/ and the Deja News archive at
-http://www.dejanews.com/ using the perl.porters-gw newsgroup, or you can
+nntp://news.perl.com/perl.porters-gw/ and the Deja archive at
+http://www.deja.com/ using the perl.porters-gw newsgroup, or you can
subscribe to the mailing list by sending perl5-porters-request@perl.org
a subscription request.
No, Perl is easy to start learning -- and easy to keep learning. It looks
like most programming languages you're likely to have experience
-with, so if you've ever written an C program, an awk script, a shell
-script, or even BASIC program, you're already part way there.
+with, so if you've ever written a C program, an awk script, a shell
+script, or even a BASIC program, you're already part way there.
Most tasks only require a small subset of the Perl language. One of
the guiding mottos for Perl development is "there's more than one way
i.e. the current interpreter. Hence Tom's quip that "Nothing but perl
can parse Perl." You may or may not choose to follow this usage. For
example, parallelism means "awk and perl" and "Python and Perl" look
-ok, while "awk and Perl" and "Python and perl" do not. But never
-write "PERL", because perl isn't really an acronym, aprocryphal
+OK, while "awk and Perl" and "Python and perl" do not. But never
+write "PERL", because perl isn't really an acronym, apocryphal
folklore and post-facto expansions notwithstanding.
=head2 Is it a Perl program or a Perl script?
what you give the actors. A program is what you give the audience."
Originally, a script was a canned sequence of normally interactive
-commands, that is, a chat script. Something like a uucp or ppp chat
+commands, that is, a chat script. Something like a UUCP or PPP chat
script or an expect script fits the bill nicely, as do configuration
scripts run by a program at its start up, such F<.cshrc> or F<.ircrc>,
for example. Chat scripts were just drivers for existing programs,
Now that "script" and "scripting" are terms that have been seized by
unscrupulous or unknowing marketeers for their own nefarious purposes,
they have begun to take on strange and often pejorative meanings,
-like "non serious" or "not real programming". Consequently, some perl
+like "non serious" or "not real programming". Consequently, some Perl
programmers prefer to avoid them altogether.
=head2 What is a JAPH?
=head2 How can I convince my sysadmin/supervisor/employees to use version (5/5.005/Perl instead of some other language)?
If your manager or employees are wary of unsupported software, or
-software which doesn't officially ship with your Operating System, you
+software which doesn't officially ship with your operating system, you
might try to appeal to their self-interest. If programmers can be
more productive using and utilizing Perl constructs, functionality,
simplicity, and power, then the typical manager/supervisor/employee
number of modules and extensions which greatly reduce development time
for any given task. Also mention that the difference between version
4 and version 5 of Perl is like the difference between awk and C++.
-(Well, ok, maybe not quite that distinct, but you get the idea.) If you
+(Well, OK, maybe not quite that distinct, but you get the idea.) If you
want support and a reasonable guarantee that what you're developing
will continue to work in the future, then you have to run the supported
version. That probably means running the 5.005 release, although 5.004
isn't that bad. Several important bugs were fixed from the 5.000 through
5.003 versions, though, so try upgrading past them if possible.
-Of particular note is the massive bughunt for buffer overflow
+Of particular note is the massive bug hunt for buffer overflow
problems that went into the 5.004 release. All releases prior to
that, including perl4, are considered insecure and should be upgraded
as soon as possible.
=head1 AUTHOR AND COPYRIGHT
-Copyright (c) 1997, 1998 Tom Christiansen and Nathan Torkington.
+Copyright (c) 1997, 1998, 1999 Tom Christiansen and Nathan Torkington.
All rights reserved.
When included as an integrated part of the Standard Distribution
covered under Perl's Artistic Licence. For separate distributions of
all or part of this FAQ outside of that, see L<perlfaq>.
-Irrespective of its distribution, all code examples here are public
+Irrespective of its distribution, all code examples here are in the public
domain. You are permitted and encouraged to use this code and any
derivatives thereof in your own programs for fun or for profit as you
see fit. A simple comment in the code giving credit to the FAQ would
Perl builds and runs on a bewildering number of platforms. Virtually
all known and current Unix derivatives are supported (Perl's native
-platform), as are proprietary systems like VMS, DOS, OS/2, Windows,
+platform), as are other systems like VMS, DOS, OS/2, Windows,
QNX, BeOS, and the Amiga. There are also the beginnings of support
for MPE/iX.
http://www.perl.com/latest/
http://www.perl.com/CPAN/ports/
-Someone looking for a Perl for Win16 might look to LMOLNAR's djgpp
+Someone looking for a Perl for Win16 might look to Laszlo Molnar's djgpp
port in http://www.perl.com/CPAN/ports/msdos/ , which comes with clear
installation instructions. A simple installation guide for MS-DOS using
-IlyaZ's OS/2 port is available at http://www.cs.ruu.nl/~piet/perl5dos.html
-and similarly for Windows 3.1 at http://www.cs.ruu.nl/~piet/perlwin3.html .
+Ilya Zakharevich's OS/2 port is available at
+http://www.cs.ruu.nl/%7Epiet/perl5dos.html
+and similarly for Windows 3.1 at http://www.cs.ruu.nl/%7Epiet/perlwin3.html .
=head2 I don't have a C compiler on my system. How can I compile perl?
If this command lists any paths which don't exist on your system, then you
may need to move the appropriate libraries to these locations, or create
-symlinks, aliases, or shortcuts appropriately. @INC is also printed as
+symbolic links, aliases, or shortcuts appropriately. @INC is also printed as
part of the output of
% perl -V
Considering that there are hundreds of existing modules in the
archive, one probably exists to do nearly anything you can think of.
-Current categories under CPAN/modules/by-category/ include perl core
+Current categories under CPAN/modules/by-category/ include Perl core
modules; development support; operating system interfaces; networking,
devices, and interprocess communication; data type utilities; database
interfaces; user interfaces; interfaces to other languages; filenames,
=head2 Where can I get information on Perl?
-The complete Perl documentation is available with the perl distribution.
-If you have perl installed locally, you probably have the documentation
+The complete Perl documentation is available with the Perl distribution.
+If you have Perl installed locally, you probably have the documentation
installed as well: type C<man perl> if you're on a system resembling Unix.
This will lead you to other important man pages, including how to set your
$MANPATH. If you're not on a Unix system, access to the documentation
will be different; for example, it might be only in HTML format. But all
-proper perl installations have fully-accessible documentation.
+proper Perl installations have fully-accessible documentation.
You might also try C<perldoc perl> in case your system doesn't
have a proper man command, or it's been misinstalled. If that doesn't
http://language.perl.com/info/documentation.html
http://reference.perl.com/query.cgi?tutorials
-=head2 What are the Perl newsgroups on USENET? Where do I post questions?
+=head2 What are the Perl newsgroups on Usenet? Where do I post questions?
The now defunct comp.lang.perl newsgroup has been superseded by the
following groups:
comp.infosystems.www.authoring.cgi Writing CGI scripts for the Web.
-There is also USENET gateway to the mailing list used by the crack
+There is also Usenet gateway to the mailing list used by the crack
Perl development team (perl5-porters) at
news://news.perl.com/perl.porters-gw/ .
including setting the Followup-To header line to NOT include alt.sources;
see their FAQ (http://www.faqs.org/faqs/alt-sources-intro/) for details.
-If you're just looking for software, first use Alta Vista, Deja News, and
+If you're just looking for software, first use AltaVista
+(http://www.altavista.com), Deja (http://www.deja.com), and
search CPAN. This is faster and more productive than just posting
a request.
=head2 Perl Books
A number of books on Perl and/or CGI programming are available. A few of
-these are good, some are ok, but many aren't worth your money. Tom
+these are good, some are OK, but many aren't worth your money. Tom
Christiansen maintains a list of these books, some with extensive
reviews, at http://www.perl.com/perl/critiques/index.html.
by Larry Wall, Tom Christiansen, and Randal L. Schwartz
*Perl 5 Desktop Reference
- By Johan Vromans
+ by Johan Vromans
+
+ *Perl in a Nutshell
+ by Ellen Siever, Stephan Spainhour, and Nathan Patwardhan
=item Tutorials
How to Set up and Maintain a World Wide Web Site [2nd edition]
by Lincoln Stein
+ *Learning Perl/Tk
+ by Nancy Walsh
+
=back
=head2 Perl in Magazines
To get the best (and possibly cheapest) performance, pick a site from
the list below and use it to grab the complete list of mirror sites.
->From there you can find the quickest site for you. Remember, the
+From there you can find the quickest site for you. Remember, the
following list is I<not> the complete list of CPAN mirrors.
http://www.perl.com/CPAN-local
http://www.cs.ruu.nl/pub/PERL/CPAN/
ftp://ftp.cs.colorado.edu/pub/perl/CPAN/
-=head2 What mailing lists are there for perl?
+=head2 What mailing lists are there for Perl?
-Most of the major modules (tk, CGI, libwww-perl) have their own
+Most of the major modules (Tk, CGI, libwww-perl) have their own
mailing lists. Consult the documentation that came with the module for
subscription information. The Perl Institute attempts to maintain a
list of mailing lists at:
=head2 Archives of comp.lang.perl.misc
-Have you tried Deja News or Alta Vista? Those are the
+Have you tried Deja or AltaVista? Those are the
best archives. Just look up "*perl*" as a newsgroup.
- http://www.dejanews.com/dnquery.xp?QRY=&DBS=2&ST=PS&defaultOp=AND&LNG=ALL&format=terse&showsort=date&maxhits=25&subjects=&groups=*perl*&authors=&fromdate=&todate=
+ http://www.deja.com/dnquery.xp?QRY=&DBS=2&ST=PS&defaultOp=AND&LNG=ALL&format=terse&showsort=date&maxhits=25&subjects=&groups=*perl*&authors=&fromdate=&todate=
You'll probably want to trim that down a bit, though.
However, these answers may not suffice for managers who require a
purchase order from a company whom they can sue should anything go awry.
Or maybe they need very serious hand-holding and contractual obligations.
-Shrink-wrapped CDs with perl on them are available from several sources if
-that will help. For example, many perl books carry a perl distribution
+Shrink-wrapped CDs with Perl on them are available from several sources if
+that will help. For example, many Perl books carry a Perl distribution
on them, as do the O'Reilly Perl Resource Kits (in both the Unix flavor
and in the proprietary Microsoft flavor); the free Unix distributions
also all come with Perl.
=head2 Where do I send bug reports?
If you are reporting a bug in the perl interpreter or the modules
-shipped with perl, use the I<perlbug> program in the perl distribution or
+shipped with Perl, use the I<perlbug> program in the Perl distribution or
mail your report to perlbug@perl.com .
If you are posting a bug with a non-standard port (see the answer to
public service long before perl.org came about. Despite the name, it's a
pretty non-commercial site meant to be a clearinghouse for information
about all things Perlian, accepting no paid advertisements, bouncy
-happy gifs, or silly java applets on its pages. The Perl Home Page at
+happy GIFs, or silly Java applets on its pages. The Perl Home Page at
http://www.perl.com/ is currently hosted on a T3 line courtesy of Songline
Systems, a software-oriented subsidiary of O'Reilly and Associates.
Other starting points include
covered under Perl's Artistic License. For separate distributions of
all or part of this FAQ outside of that, see L<perlfaq>.
-Irrespective of its distribution, all code examples here are public
+Irrespective of its distribution, all code examples here are in the public
domain. You are permitted and encouraged to use this code and any
derivatives thereof in your own programs for fun or for profit as you
see fit. A simple comment in the code giving credit to the FAQ would
Various http://www.perl.com/CPAN/doc/FMTEYEWTK/index.html
(not a man-page but still useful)
-L<perltoc> provides a crude table of contents for the perl man page set.
+A crude table of contents for the Perl man page set is found in L<perltoc>.
=head2 How can I use Perl interactively?
=head2 Is there a Perl shell?
-In general, no. The Shell.pm module (distributed with perl) makes
-perl try commands which aren't part of the Perl language as shell
+In general, no. The Shell.pm module (distributed with Perl) makes
+Perl try commands which aren't part of the Perl language as shell
commands. perlsh from the source distribution is simplistic and
uninteresting, but may still be what you want.
http://www.perl.com/CPAN/doc/misc/tips/working.vgrind.entry, but the
results are not particularly satisfying for sophisticated code.
-The a2ps at http://www.infres.enst.fr/~demaille/a2ps/ does lots of things
+The a2ps at http://www.infres.enst.fr/%7Edemaille/a2ps/ does lots of things
related to generating nicely printed output of documents.
=head2 Is there a ctags for Perl?
PerlBuilder (XXX URL to follow) is an integrated development environment
for Windows that supports Perl development. Perl programs are just plain
text, though, so you could download emacs for Windows (???) or a vi clone
-(vim) which runs on for win32 (http://www.cs.vu.nl/~tmgil/vi.html).
+(vim) which runs on for win32 (http://www.cs.vu.nl/%7Etmgil/vi.html).
If you're transferring Windows files to Unix, be sure to transfer in
ASCII mode so the ends of lines are appropriately mangled.
=head2 Where can I get perl-mode for emacs?
Since Emacs version 19 patchlevel 22 or so, there have been both a
-perl-mode.el and support for the perl debugger built in. These should
+perl-mode.el and support for the Perl debugger built in. These should
come with the standard Emacs 19 distribution.
-In the perl source directory, you'll find a directory called "emacs",
+In the Perl source directory, you'll find a directory called "emacs",
which contains a cperl-mode that color-codes keywords, provides
context-sensitive help, and other nifty things.
directory http://www.perl.com/CPAN/modules/by-category/08_User_Interfaces/
Invaluable for Perl/Tk programming are: the Perl/Tk FAQ at
-http://w4.lns.cornell.edu/~pvhp/ptk/ptkTOC.html , the Perl/Tk Reference
+http://w4.lns.cornell.edu/%7Epvhp/ptk/ptkTOC.html , the Perl/Tk Reference
Guide available at
http://www.perl.com/CPAN-local/authors/Stephen_O_Lidie/ , and the
online manpages at
-http://www-users.cs.umn.edu/~amundson/perl/perltk/toc.html .
+http://www-users.cs.umn.edu/%7Eamundson/perl/perltk/toc.html .
=head2 How can I generate simple menus without using CGI or Tk?
information.
Unsubstantiated reports allege that Perl interpreters that use sfio
-outperform those that don't (for IO intensive applications). To try
+outperform those that don't (for I/O intensive applications). To try
this, see the F<INSTALL> file in the source distribution, especially
-the ``Selecting File IO mechanisms'' section.
+the ``Selecting File I/O mechanisms'' section.
The undump program was an old attempt to speed up your Perl program
by storing the already-compiled form to disk. This is no longer
http://perl.apache.org/
With the FCGI module (from CPAN) and the mod_fastcgi
-module (available from http://www.fastcgi.com/) each of your perl
-scripts becomes a permanent CGI daemon process.
+module (available from http://www.fastcgi.com/) each of your Perl
+programs becomes a permanent CGI daemon process.
Both of these solutions can have far-reaching effects on your system
-and on the way you write your CGI scripts, so investigate them with
+and on the way you write your CGI programs, so investigate them with
care.
See http://www.perl.com/CPAN/modules/by-category/15_World_Wide_Web_HTML_HTTP_CGI/ .
A non-free, commercial product, ``The Velocity Engine for Perl'',
(http://www.binevolve.com/ or http://www.binevolve.com/bine/vep) might
also be worth looking at. It will allow you to increase the performance
-of your perl scripts, upto 25 times faster than normal CGI perl by
-running in persistent perl mode, or 4 to 5 times faster without any
-modification to your existing CGI scripts. Fully functional evaluation
+of your Perl programs, up to 25 times faster than normal CGI Perl by
+running in persistent Perl mode, or 4 to 5 times faster without any
+modification to your existing CGI programs. Fully functional evaluation
copies are available from the web site.
=head2 How can I hide the source for my Perl program?
because as currently written, all programs are prepared for a full
eval() statement. You can tremendously reduce this cost by building a
shared I<libperl.so> library and linking against that. See the
-F<INSTALL> podfile in the perl source distribution for details. If
+F<INSTALL> podfile in the Perl source distribution for details. If
you link your main perl binary with this, it will make it minuscule.
For example, on one author's system, F</usr/bin/perl> is only 11k in
size!
You can't. Not yet, anyway. You can integrate Java and Perl with the
Perl Resource Kit from O'Reilly and Associates. See
http://www.oreilly.com/catalog/prkunix/ for more information.
-The Java interface will be supported in the core 5.006 release
+The Java interface will be supported in the core 5.6 release
of Perl.
=head2 How can I get C<#!perl> to work on [MS-DOS,NT,...]?
interpreter, NT people can use: C<SET PATHEXT=%PATHEXT%;.PL> to let them
run the program C<install-linux.pl> merely by typing C<install-linux>.
-Macintosh perl scripts will have the appropriate Creator and
-Type, so that double-clicking them will invoke the perl application.
+Macintosh Perl programs will have the appropriate Creator and
+Type, so that double-clicking them will invoke the Perl application.
I<IMPORTANT!>: Whatever you do, PLEASE don't get frustrated, and just
throw the perl interpreter into your cgi-bin directory, in order to
-get your scripts working for a web server. This is an EXTREMELY big
+get your programs working for a web server. This is an EXTREMELY big
security risk. Take the time to figure out how to do it correctly.
-=head2 Can I write useful perl programs on the command line?
+=head2 Can I write useful Perl programs on the command line?
Yes. Read L<perlrun> for more information. Some examples follow.
(These assume standard Unix shell quoting rules.)
echo $PATH | perl -nl -072 -e '
s![^/+]*$!man!&&-d&&!$s{$_}++&&push@m,$_;END{print"@m"}'
-Ok, the last one was actually an obfuscated perl entry. :-)
+OK, the last one was actually an Obfuscated Perl Contest entry. :-)
-=head2 Why don't perl one-liners work on my DOS/Mac/VMS system?
+=head2 Why don't Perl one-liners work on my DOS/Mac/VMS system?
The problem is usually that the command interpreters on those systems
have rather different ideas about quoting than the Unix shells under
=head2 Where can I learn about object-oriented Perl programming?
-
L<perltoot> is a good place to start, and you can use L<perlobj> and
+
A good place to start is L<perltoot>, and you can use L<perlobj> and
L<perlbot> for reference. Perltoot didn't come out until the 5.004
release, but you can get a copy (in pod, html, or postscript) from
http://www.perl.com/CPAN/doc/FMTEYEWTK/ .
Download the ExtUtils::Embed kit from CPAN and run `make test'. If
the tests pass, read the pods again and again and again. If they
-fail, see L<perlbug> and send a bugreport with the output of
+fail, see L<perlbug> and send a bug report with the output of
C<make test TEST_VERBOSE=1> along with C<perl -V>.
=head2 When I tried to run my script, I got this message. What does it
mean?
-L<perldiag> has a complete list of perl's error messages and warnings,
-with explanatory text. You can also use the splain program (distributed
-with perl) to explain the error messages:
+A complete list of Perl's error messages and warnings with explanatory
+text can be found in L<perldiag>. You can also use the splain program
+(distributed with Perl) to explain the error messages:
perl program 2>diag.out
splain [-v] [-p] diag.out
=head2 What's MakeMaker?
-This module (part of the standard perl distribution) is designed to
+This module (part of the standard Perl distribution) is designed to
write a Makefile for an extension module from a Makefile.PL. For more
information, see L<ExtUtils::MakeMaker>.
covered under Perl's Artistic License. For separate distributions of
all or part of this FAQ outside of that, see L<perlfaq>.
-Irrespective of its distribution, all code examples here are public
+Irrespective of its distribution, all code examples here are in the public
domain. You are permitted and encouraged to use this code and any
derivatives thereof in your own programs for fun or for profit as you
see fit. A simple comment in the code giving credit to the FAQ would
are displayed in either the format you specify with printf(), or the
current output format for numbers (see L<perlvar/"$#"> if you use
print. C<$#> has a different default value in Perl5 than it did in
-Perl4. Changing C<$#> yourself is deprecated.
+Perl4. Changing C<$#> yourself is deprecated.)
This affects B<all> computer languages that represent decimal
floating-point numbers in binary, not just Perl. Perl provides
printf("%.3f", 3.1415926535); # prints 3.142
-The POSIX module (part of the standard perl distribution) implements
+The POSIX module (part of the standard Perl distribution) implements
ceil(), floor(), and a number of other mathematical and trigonometric
functions.
$floor = floor(3.5); # 3
In 5.000 to 5.003 Perls, trigonometry was done in the Math::Complex
-module. With 5.004, the Math::Trig module (part of the standard perl
+module. With 5.004, the Math::Trig module (part of the standard Perl
distribution) implements the trigonometric functions. Internally it
uses the Math::Complex module and some functions can break out from
the real axis into the complex plane, for example the inverse sine of
To turn a string of 1s and 0s like C<10110110> into a scalar containing
its binary value, use the pack() and unpack() functions (documented in
-L<perlfunc/"pack" L<perlfunc/"unpack">):
+L<perlfunc/"pack"
> and L<perlfunc/"unpack">):
$decimal = unpack('c', pack('B8', '10110110'));
This packs the string C<10110110> into an eight bit binary structure.
-This is then unpack as a character, which returns its ordinal value.
+This is then unpacked as a character, which returns its ordinal value.
This does the same thing:
push(@results, some_func($i));
}
+This situation has been fixed in Perl5.005. Use of C<..> in a C<for>
+loop will iterate over the range, without creating the entire range.
+
+ for my $i (5 .. 500_005) {
+ push(@results, some_func($i));
+ }
+
+will not create a list of 500,000 integers.
+
=head2 How can I output Roman numerals?
Get the http://www.perl.com/CPAN/modules/by-module/Roman module.
#
# The explicit settings of $ndst and $tdst are necessary because localtime
# only says it returns the system tm struct, and the system tm struct at
- # least on Solaris doesn't guarantee any particuliar positive value (like,
+ # least on Solaris doesn't guarantee any particular positive value (like,
# say, 1) for isdst, just a positive value. And that value can
# potentially be negative, if DST information isn't available (this sub
# just treats those cases like no DST).
# Copyright relinquished 1999 by Russ Allbery <rra@stanford.edu>
# This code is in the public domain
-=head2 Does Perl have a year 2000 problem? Is Perl Y2K compliant?
+=head2 Does Perl have a Year 2000 problem? Is Perl Y2K compliant?
Short answer: No, Perl does not have a Year 2000 problem. Yes, Perl is
Y2K compliant (whatever that means). The programmers you've hired to
Can you use your pencil to write a non-Y2K-compliant memo? Of course
you can. Is that the pencil's fault? Of course it isn't.
-The date and time functions supplied with perl (gmtime and localtime)
+The date and time functions supplied with Perl (gmtime and localtime)
supply adequate information to determine the year well beyond 2000
(2038 is when trouble strikes for 32-bit machines). The year returned
by these functions when used in an array context is the year minus 1900.
modules or oddities that will make your life a lot easier. There is
the CPAN module Parse::RecDescent, the standard module Text::Balanced,
the byacc program, the CPAN module Parse::Yapp, and Mark-Jason
-Dominus's excellent I<py> tool at http://www.plover.com/~mjd/perl/py/
+Dominus's excellent I<py> tool at http://www.plover.com/%7Emjd/perl/py/
.
One simple destructive, inside-out approach that you might try is to
1 while $string =~ s/\t+/' ' x (length($&) * 8 - length($`) % 8)/e;
-Or you can just use the Text::Tabs module (part of the standard perl
+Or you can just use the Text::Tabs module (part of the standard Perl
distribution).
use Text::Tabs;
=head2 How do I reformat a paragraph?
-Use Text::Wrap (part of the standard perl distribution):
+Use Text::Wrap (part of the standard Perl distribution):
use Text::Wrap;
print wrap("\t", ' ', @paragraphs);
$line =~ s/\b(\w)/\U$1/g;
This has the strange effect of turning "C<don't do it>" into "C<Don'T
-Do It>". Sometimes you might want this, instead (Suggested by Brian
-Foy):
+Do It>". Sometimes you might want this, instead (Suggested by brian d.
+foy):
$string =~ s/ (
(^\w) #at the beginning of the line
C<"like \"this\"">. Unescaping them is a task addressed earlier in
this section.
-Alternatively, the Text::ParseWords module (part of the standard perl
+Alternatively, the Text::ParseWords module (part of the standard Perl
distribution) lets you say:
use Text::ParseWords;
=head2 How do I find the soundex value of a string?
-Use the standard Text::Soundex module distributed with perl.
+Use the standard Text::Soundex module distributed with Perl.
But before you do so, you may want to determine whether `soundex' is in
fact what you think it is. Knuth's soundex algorithm compresses words
into a small space, and so it does not necessarily distinguish between
This is nice in that it doesn't use much extra memory, simulating
uniq(1)'s behavior of removing only adjacent duplicates. It's less
nice in that it won't work with false values like undef, 0, or "";
-"0 but true" is ok, though.
+"0 but true" is OK, though.
=item b) If you don't know whether @in is sorted:
undef @ary;
@ary[@in] = @in;
- @out = @ary;
+ @out = grep {defined} @ary;
=back
In general, you usually don't need a linked list in Perl, since with
regular arrays, you can push and pop or shift and unshift at either end,
or you can use splice to add and/or remove arbitrary number of elements at
-arbitrary points. Both pop and shift are both O(1) operations on perl's
+arbitrary points. Both pop and shift are both O(1) operations on Perl's
dynamic arrays. In the absence of shifts and pops, push in general
needs to reallocate on the order every log(N) times, and unshift will
need to copy pointers each time.
Don't do that. :-)
[lwall] In Perl 4, you were not allowed to modify a hash at all while
-interating over it. In Perl 5 you can delete from it, but you still
+iterating over it. In Perl 5 you can delete from it, but you still
can't add to it, because that might cause a doubling of the hash table,
in which half the entries get copied up to the new top half of the
-table, at which point you've totally bamboozled the interator code.
+table, at which point you've totally bamboozled the iterator code.
Even if the table doesn't double, there's no telling whether your new
entry will be inserted before or after the current iterator position.
$ary{'d'} is false
defined $ary{'d'} is true
defined $ary{'a'} is true
- exists $ary{'a'} is true (perl5 only)
+ exists $ary{'a'} is true (Perl5 only)
grep ($_ eq 'a', keys %ary) is true
If you now say
$ary{'d'} is false
defined $ary{'d'} is true
defined $ary{'a'} is FALSE
- exists $ary{'a'} is true (perl5 only)
+ exists $ary{'a'} is true (Perl5 only)
grep ($_ eq 'a', keys %ary) is true
Notice the last two: you have an undef value, but a defined key!
$ary{'d'} is false
defined $ary{'d'} is true
defined $ary{'a'} is false
- exists $ary{'a'} is FALSE (perl5 only)
+ exists $ary{'a'} is FALSE (Perl5 only)
grep ($_ eq 'a', keys %ary) is FALSE
See, the whole entry is gone!
get scalars passed in by reference. If somefunc() modifies C<$_[0]>,
it has to be ready to write it back into the caller's version.
-This has been fixed as of perl5.004.
+This has been fixed as of Perl5.004.
Normally, merely accessing a key's value for a nonexistent key does
I<not> cause that key to be forever there. This is different than
=head2 How can I use a reference as a hash key?
You can't do this directly, but you could use the standard Tie::Refhash
-module distributed with perl.
+module distributed with Perl.
=head1 Data: Misc
successful create or unlink the same file! Therefore O_EXCL
isn't so exclusive as you might wish.
-See also the new L<perlopentut> if you have it (new for 5.006).
+See also the new L<perlopentut> if you have it (new for 5.6).
=head2 Why do I sometimes get an "Argument list too long" when I use E<lt>*E<gt>?
or die "can't open $badpath: $!";
For more information, see also the new L<perlopentut> if you have it
-(new for 5.006).
+(new for 5.6).
=head2 How can I reliably rename a file?
your getting your job done.)
For more information on file locking, see also L<perlopentut/"File
-Locking"> if you have it (new for 5.006).
+Locking"> if you have it (new for 5.6).
=back
@lines = `cat $file`;
-This tiny but expedient solution is neat, clean, and portable to all
-systems that you've bothered to install decent tools on, even if you are
-a Prisoner of Bill. For those die-hards PoBs who've paid their billtax
-and refuse to use the toolbox, or who like writing complicated code for
-job security, you can of course read the file manually.
+This tiny but expedient solution is neat, clean, and portable to
+all systems on which decent tools have been installed. For those
+who prefer not to use the toolbox, you can of course read the file
+manually, although this makes for more complicated code.
{
local(*INPUT, $/);
covered under Perl's Artistic License. For separate distributions of
all or part of this FAQ outside of that, see L<perlfaq>.
-Irrespective of its distribution, all code examples here are public
+Irrespective of its distribution, all code examples here are in the public
domain. You are permitted and encouraged to use this code and any
derivatives thereof in your own programs for fun or for profit as you
see fit. A simple comment in the code giving credit to the FAQ would
themselves abort the exit. Likewise any object destructors that need to
be called are called before the real exit. If this is a problem, you
can call C<POSIX:_exit($status)> to avoid END and destructor processing.
-See L<perlsub> for details.
+See L<perlmod> for details.
=item exp EXPR
value: the CODE ref of the closure you just created. See L<perlsub> and
L<perlref> for details.
-=item substr EXPR,OFFSET,LEN,REPLACEMENT
+=item substr EXPR,OFFSET,LENGTH,REPLACEMENT
-=item substr EXPR,OFFSET,LEN
+=item substr EXPR,OFFSET,LENGTH
=item substr EXPR,OFFSET
Extracts a substring out of EXPR and returns it. First character is at
offset C<0>, or whatever you've set C<$[> to (but don't do that).
If OFFSET is negative (or more precisely, less than C<$[>), starts
-that far from the end of the string. If LEN is omitted, returns
-everything to the end of the string. If LEN is negative, leaves that
+that far from the end of the string. If LENGTH is omitted, returns
+everything to the end of the string. If LENGTH is negative, leaves that
many characters off the end of the string.
-If you specify a substring that is partly outside the string, the part
-within the string is returned. If the substring is totally outside
-the string a warning is produced.
-
You can use the substr() function as an lvalue, in which case EXPR
-must itself be an lvalue. If you assign something shorter than LEN,
-the string will shrink, and if you assign something longer than LEN,
+must itself be an lvalue. If you assign something shorter than LENGTH,
+the string will shrink, and if you assign something longer than LENGTH,
the string will grow to accommodate it. To keep the string the same
length you may need to pad or chop your value using C<sprintf>.
+If OFFSET and LENGTH specify a substring that is partly outside the
+string, only the part within the string is returned. If the substring
+is beyond either end of the string, substr() returns the undefined
+value and produces a warning. When used as an lvalue, specifying a
+substring that is entirely outside the string is a fatal error.
+Here's an example showing the behavior for boundary cases:
+
+ my $name = 'fred';
+ substr($name, 4) = 'dy'; # $name is now 'freddy'
+ my $null = substr $name, 6, 2; # returns '' (no warning)
+ my $oops = substr $name, 7; # returns undef, with warning
+ substr($name, 7) = 'gap'; # fatal error
+
An alternative to using substr() as an lvalue is to specify the
replacement string as the 4th argument. This allows you to replace
parts of the EXPR and return what was there before in one operation,
hash = 0;
while (klen--)
hash = (hash * 33) + *key++;
- hash = hash + (hash >> 5); /* after 5.006 */
+ hash = hash + (hash >> 5); /* after 5.6 */
-The last step was added in version 5.006 to improve distribution of
+The last step was added in version 5.6 to improve distribution of
lower bits in the resulting hash value.
See L<Understanding the Magic of Tied Hashes and Arrays> for more
5.005_03-MT5 1999-Jan-28
5.005_03 1999-Mar-28
- Sarathy 5.005_50 1998-Jul-26 The 5.006 development track.
+ Sarathy 5.005_50 1998-Jul-26 The 5.6 development track.
5.005_51 1998-Aug-10
5.005_52 1998-Sep-25
5.005_53 1998-Oct-31
pattern matching capabilities. Perl provides customary quote characters
for these behaviors, but also provides a way for you to choose your
quote character for any of them. In the following table, a C<{}> represents
-any pair of delimiters you choose. Non-bracketing delimiters use
-the same character fore and aft, but the 4 sorts of brackets
-(round, angle, square, curly) will all nest.
+any pair of delimiters you choose.
Customary Generic Meaning Interpolates
'' q{} Literal no
s{}{} Substitution yes (unless '' is delimiter)
tr{}{} Transliteration no (but see below)
+Non-bracketing delimiters use the same character fore and aft, but the four
+sorts of brackets (round, angle, square, curly) will all nest, which means
+that
+
+ q{foo{bar}baz}
+
+is the same as
+
+ 'foo{bar}baz'
+
+Note, however, that this does not always work for quoting Perl code:
+
+ $s = q{ if($a eq "}") ... }; # WRONG
+
+is a syntax error. The C<Text::Balanced> module on CPAN is able to do this
+properly.
+
There can be whitespace between the operator and the quoting
characters, except when C<#> is being used as the quoting character.
C<q#foo#> is parsed as the string C<foo>, while C<q #foo#> is the
S<Mac OS X Server> and its Open Source version, Darwin, both run Unix
perl natively (with a few patches). Full support for these
-is slated for perl5.006.
+is slated for perl 5.6.
Also see:
=head2 Making my() work on "package" variables
Being able to say my($Foo::Bar), something that sounds ludicrous and
-the 5.006 pumpking has mocked.
+the 5.6 pumpking has mocked.
=head2 "or" testing defined not truth
sub exclaim {
my $self = shift;
return sprintf "Hi, I'm %s, age %d, working with %s",
- $self->{NAME}, $self->{AGE}, join(", ", $self->{PEERS});
+ $self->{NAME}, $self->{AGE}, join(", ", @{$self->{PEERS}});
}
Or maybe even one like this:
Both these problems can be easily fixed. Just add the C<use strict>
pragma, then pre-declare your package variables. (The C<our> operator
-will be new in 5.006, and will work for package globals just like C<my>
+will be new in 5.6, and will work for package globals just like C<my>
works for scoped lexicals.)
package Some_Class;
use strict;
- our($CData1, $CData2); # our() is new to perl5.006
+ our($CData1, $CData2); # our() is new to perl5.6
sub CData1 {
shift; # XXX: ignore calling class/object
$CData1 = shift if @_;
package Some_Class;
use strict;
- our %ClassData = ( # our() is new to perl5.006
+ our %ClassData = ( # our() is new to perl5.6
CData1 => "",
CData2 => "",
);
use strict;
# create class meta-object using that most perfect of names
- our %Some_Class = ( # our() is new to perl5.006
+ our %Some_Class = ( # our() is new to perl5.6
CData1 => "",
CData2 => "",
);
package Some_Class;
use strict;
- our %Some_Class = ( # our() is new to perl5.006
+ our %Some_Class = ( # our() is new to perl5.6
CData1 => "",
CData2 => "",
);
haven't thought of before.
package Some_Class;
- our($CData1, $CData2); # our() is new to perl5.006
+ our($CData1, $CData2); # our() is new to perl5.6
sub new {
my $obclass = shift;
package Some_Class;
use strict;
- our %Some_Class = ( # our() is new to perl5.006
+ our %Some_Class = ( # our() is new to perl5.6
CData1 => "",
CData2 => "",
);
variables, user and group IDs, or the current working directory are
treated across a fork(). You can change only yourself, but you will see
those changes reflected in your unspawned children. Changes to one object
-will propagate enither up to the parent nor down to any existing child objects.
+will propagate neither up to the parent nor down to any existing child objects.
Those objects made later, however, will see the changes.
If you have an object with an actual attribute value, and you want to
# so the latter can be used for both initialization
# and translucency.
- our %Vermin = ( # our() is new to perl5.006
+ our %Vermin = ( # our() is new to perl5.6
PopCount => 0, # capital for class attributes
color => "beige", # small for instance attributes
);
No one--absolutely no one--is allowed to read or write the class
attributes without the mediation of the managing accessor method, since
only that method has access to the lexical variable it's managing.
-This use of mediated access to class attributes is a form privacy far
+This use of mediated access to class attributes is a form of privacy far
stronger than most OO languages provide.
The repetition of code used to create per-datum accessor methods chafes
=head2 Translucency Revisited
-The Vermin class used to demonstrate translucency used an eponymously
-named package variable, %Vermin, as its meta-object. If you prefer to
+The Vermin class demonstrates translucency using a package variable,
+eponymously named %Vermin, as its meta-object. If you prefer to
use absolutely no package variables beyond those necessary to appease
inheritance or possibly the Exporter, this strategy is closed to you.
That's too bad, because translucent attributes are an appealing
We use the hypothetical our() syntax for package variables. It works
like C<use vars>, but looks like my(). It should be in this summer's
-major release (5.006) of perl--we hope.
+major release (5.6) of perl--we hope.
You can't use file-scoped lexicals in conjunction with the SelfLoader
or the AutoLoader, because they alter the lexical scope in which the
a reference, you'll raise a run-time exception.
The following list is ordered by scalar variables first, then the
-arrays, then the hashes (except $^M was added in the wrong place).
-This is somewhat obscured because %ENV and %SIG are listed as
-$ENV{expr} and $SIG{expr}.
+arrays, then the hashes.
=over 8
C<do>, C<require>, or C<use> operators. The key is the filename
you specified (with module names converted to pathnames), and the
value is the location of the file found. The C<require>
-operator uses this array to determine whether a particular file has
+operator uses this hash to determine whether a particular file has
already been included.
=item %ENV
control-C<W>. This is better than typing a literal control-C<W>
into your program.
-Finally, new in Perl 5.006, Perl variable names may be alphanumeric
+Finally, new in Perl 5.6, Perl variable names may be alphanumeric
strings that begin with control characters (or better yet, a caret).
These variables must be written in the form C<${^Foo}>; the braces
are not optional. C<${^Foo}> denotes the scalar variable whose
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