=head1 NAME
-perlfaq3 - Programming Tools ($Revision: 1.47 $, $Date: 2005/03/27 07:21:22 $)
+perlfaq3 - Programming Tools
=head1 DESCRIPTION
=head2 How can I use Perl interactively?
The typical approach uses the Perl debugger, described in the
-perldebug(1) manpage, on an ``empty'' program, like this:
+C<perldebug(1)> manpage, on an "empty" program, like this:
perl -de 42
=head2 Is there a Perl shell?
-The psh (Perl sh) is currently at version 1.8. The Perl Shell is a
-shell that combines the interactive nature of a Unix shell with the
-power of Perl. The goal is a full featured shell that behaves as
-expected for normal shell activity and uses Perl syntax and
-functionality for control-flow statements and other things.
-You can get psh at http://www.focusresearch.com/gregor/psh/ .
+The C<psh> (Perl sh) is currently at version 1.8. The Perl Shell is a shell
+that combines the interactive nature of a Unix shell with the power of
+Perl. The goal is a full-featured shell that behaves as expected for
+normal shell activity and uses Perl syntax and functionality for
+control-flow statements and other things. You can get C<psh> at
+http://sourceforge.net/projects/psh/ .
-Zoidberg is a similar project and provides a shell written in perl,
+C<Zoidberg> is a similar project and provides a shell written in perl,
configured in perl and operated in perl. It is intended as a login shell
-and development environment. It can be found at http://zoidberg.sf.net/
+and development environment. It can be found at
+http://pardus-larus.student.utwente.nl/~pardus/projects/zoidberg/
or your local CPAN mirror.
-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.
+The C<Shell.pm> module (distributed with Perl) makes Perl try commands
+which aren't part of the Perl language as shell commands. C<perlsh> from
+the source distribution is simplistic and uninteresting, but may still
+be what you want.
=head2 How do I find which modules are installed on my system?
-You can use the ExtUtils::Installed module to show all
-installed distributions, although it can take awhile to do
-its magic. The standard library which comes with Perl just
-shows up as "Perl" (although you can get those with
-Module::CoreList).
+From the command line, you can use the C<cpan> command's C<-l> switch:
+
+ $ cpan -l
+
+You can also use C<cpan>'s C<-a> switch to create an autobundle file
+that C<CPAN.pm> understands and can use to re-install every module:
+
+ $ cpan -a
+
+Inside a Perl program, you can use the C<ExtUtils::Installed> module to
+show all installed distributions, although it can take awhile to do
+its magic. The standard library which comes with Perl just shows up
+as "Perl" (although you can get those with C<Module::CoreList>).
use ExtUtils::Installed;
my @modules = $inst->modules();
If you want a list of all of the Perl module filenames, you
-can use File::Find::Rule.
+can use C<File::Find::Rule>:
use File::Find::Rule;
- my @files = File::Find::Rule->file()->name( '*.pm' )->in( @INC );
+ my @files = File::Find::Rule->
+ extras({follow => 1})->
+ file()->
+ name( '*.pm' )->
+ in( @INC )
+ ;
If you do not have that module, you can do the same thing
-with File::Find which is part of the standard library.
-
- use File::Find;
- my @files;
-
- find sub { push @files, $File::Find::name if -f _ && /\.pm$/ },
- @INC;
+with C<File::Find> which is part of the standard library:
+
+ use File::Find;
+ my @files;
+
+ find(
+ {
+ wanted => sub {
+ push @files, $File::Find::fullname
+ if -f $File::Find::fullname && /\.pm$/
+ },
+ follow => 1,
+ follow_skip => 2,
+ },
+ @INC
+ );
print join "\n", @files;
-If you simply need to quickly check to see if a module is
+If you simply need to check quickly to see if a module is
available, you can check for its documentation. If you can
read the documentation the module is most likely installed.
If you cannot read the documentation, the module might not
-have any (in rare cases).
+have any (in rare cases):
- prompt% perldoc Module::Name
+ $ perldoc Module::Name
You can also try to include the module in a one-liner to see if
-perl finds it.
+perl finds it:
- perl -MModule::Name -e1
+ $ perl -MModule::Name -e1
=head2 How do I debug my Perl programs?
-Have you tried C<use warnings> or used C<-w>? They enable warnings
-to detect dubious practices.
+(contributed by brian d foy)
+
+Before you do anything else, you can help yourself by ensuring that
+you let Perl tell you about problem areas in your code. By turning
+on warnings and strictures, you can head off many problems before
+they get too big. You can find out more about these in L<strict>
+and L<warnings>.
+
+ #!/usr/bin/perl
+ use strict;
+ use warnings;
+
+Beyond that, the simplest debugger is the C<print> function. Use it
+to look at values as you run your program:
-Have you tried C<use strict>? It prevents you from using symbolic
-references, makes you predeclare any subroutines that you call as bare
-words, and (probably most importantly) forces you to predeclare your
-variables with C<my>, C<our>, or C<use vars>.
+ print STDERR "The value is [$value]\n";
-Did you check the return values of each and every system call? The operating
-system (and thus Perl) tells you whether they worked, and if not
-why.
+The C<Data::Dumper> module can pretty-print Perl data structures:
- open(FH, "> /etc/cantwrite")
- or die "Couldn't write to /etc/cantwrite: $!\n";
+ use Data::Dumper qw( Dumper );
+ print STDERR "The hash is " . Dumper( \%hash ) . "\n";
-Did you read L<perltrap>? It's full of gotchas for old and new Perl
-programmers and even has sections for those of you who are upgrading
-from languages like I<awk> and I<C>.
+Perl comes with an interactive debugger, which you can start with the
+C<-d> switch. It's fully explained in L<perldebug>.
-Have you tried the Perl debugger, described in L<perldebug>? You can
-step through your program and see what it's doing and thus work out
-why what it's doing isn't what it should be doing.
+If you'd like a graphical user interface and you have C<Tk>, you can use
+C<ptkdb>. It's on CPAN and available for free.
+
+If you need something much more sophisticated and controllable, Leon
+Brocard's C<Devel::ebug> (which you can call with the C<-D> switch as C<-Debug>)
+gives you the programmatic hooks into everything you need to write your
+own (without too much pain and suffering).
+
+You can also use a commercial debugger such as Affrus (Mac OS X), Komodo
+from Activestate (Windows and Mac OS X), or EPIC (most platforms).
=head2 How do I profile my Perl programs?
-You should get the Devel::DProf module from the standard distribution
-(or separately on CPAN) and also use Benchmark.pm from the standard
-distribution. The Benchmark module lets you time specific portions of
-your code, while Devel::DProf gives detailed breakdowns of where your
-code spends its time.
+(contributed by brian d foy, updated Fri Jul 25 12:22:26 PDT 2008)
+
+The C<Devel> namespace has several modules which you can use to
+profile your Perl programs. The C<Devel::DProf> module comes with Perl
+and you can invoke it with the C<-d> switch:
+
+ perl -d:DProf program.pl
+
+After running your program under C<DProf>, you'll get a F<tmon.out> file
+with the profile data. To look at the data, you can turn it into a
+human-readable report with the C<dprofpp> program that comes with
+C<Devel::DProf>.
+
+ dprofpp
+
+You can also do the profiling and reporting in one step with the C<-p>
+switch to C<dprofpp>:
+
+ dprofpp -p program.pl
+
+The C<Devel::NYTProf> (New York Times Profiler) does both statement
+and subroutine profiling. It's available from CPAN and you also invoke
+it with the C<-d> switch:
-Here's a sample use of Benchmark:
+ perl -d:NYTProf some_perl.pl
- use Benchmark;
+Like C<DProf>, it creates a database of the profile information that you
+can turn into reports. The C<nytprofhtml> command turns the data into
+an HTML report similar to the C<Devel::Cover> report:
- @junk = `cat /etc/motd`;
- $count = 10_000;
+ nytprofhtml
- timethese($count, {
- 'map' => sub { my @a = @junk;
- map { s/a/b/ } @a;
- return @a },
- 'for' => sub { my @a = @junk;
- for (@a) { s/a/b/ };
- return @a },
- });
+CPAN has several other profilers that you can invoke in the same
+fashion. You might also be interested in using the C<Benchmark> to
+measure and compare code snippets.
-This is what it prints (on one machine--your results will be dependent
-on your hardware, operating system, and the load on your machine):
+You can read more about profiling in I<Programming Perl>, chapter 20,
+or I<Mastering Perl>, chapter 5.
- Benchmark: timing 10000 iterations of for, map...
- for: 4 secs ( 3.97 usr 0.01 sys = 3.98 cpu)
- map: 6 secs ( 4.97 usr 0.00 sys = 4.97 cpu)
+L<perldebguts> documents creating a custom debugger if you need to
+create a special sort of profiler. brian d foy describes the process
+in I<The Perl Journal>, "Creating a Perl Debugger",
+http://www.ddj.com/184404522 , and "Profiling in Perl"
+http://www.ddj.com/184404580 .
-Be aware that a good benchmark is very hard to write. It only tests the
-data you give it and proves little about the differing complexities
-of contrasting algorithms.
+Perl.com has two interesting articles on profiling: "Profiling Perl",
+by Simon Cozens, http://www.perl.com/lpt/a/850 and "Debugging and
+Profiling mod_perl Applications", by Frank Wiles,
+http://www.perl.com/pub/a/2006/02/09/debug_mod_perl.html .
+
+Randal L. Schwartz writes about profiling in "Speeding up Your Perl
+Programs" for I<Unix Review>,
+http://www.stonehenge.com/merlyn/UnixReview/col49.html , and "Profiling
+in Template Toolkit via Overriding" for I<Linux Magazine>,
+http://www.stonehenge.com/merlyn/LinuxMag/col75.html .
=head2 How do I cross-reference my Perl programs?
-The B::Xref module can be used to generate cross-reference reports
+The C<B::Xref> module can be used to generate cross-reference reports
for Perl programs.
perl -MO=Xref[,OPTIONS] scriptname.plx
=head2 Is there a pretty-printer (formatter) for Perl?
-Perltidy is a Perl script which indents and reformats Perl scripts
+C<Perltidy> is a Perl script which indents and reformats Perl scripts
to make them easier to read by trying to follow the rules of the
L<perlstyle>. If you write Perl scripts, or spend much time reading
them, you will probably find it useful. It is available at
-http://perltidy.sourceforge.net
+http://perltidy.sourceforge.net .
Of course, if you simply follow the guidelines in L<perlstyle>,
you shouldn't need to reformat. The habit of formatting your code
help you with this. The perl-mode or newer cperl-mode for emacs
can provide remarkable amounts of help with most (but not all)
code, and even less programmable editors can provide significant
-assistance. Tom Christiansen and many other VI users swear by
+assistance. Tom Christiansen and many other VI users swear by
the following settings in vi and its clones:
set ai sw=4
Put that in your F<.exrc> file (replacing the caret characters
with control characters) and away you go. In insert mode, ^T is
-for indenting, ^D is for undenting, and ^O is for blockdenting--
-as it were. A more complete example, with comments, can be found at
+for indenting, ^D is for undenting, and ^O is for blockdenting--as
+it were. A more complete example, with comments, can be found at
http://www.cpan.org/authors/id/TOMC/scripts/toms.exrc.gz
The a2ps http://www-inf.enst.fr/%7Edemaille/a2ps/black+white.ps.gz does
lots of things related to generating nicely printed output of
-documents, as does enscript at http://people.ssh.fi/mtr/genscript/ .
+documents.
=head2 Is there a ctags for Perl?
-Recent versions of ctags do much more than older versions did.
-EXUBERANT CTAGS is available from http://ctags.sourceforge.net/
-and does a good job of making tags files for perl code.
+(contributed by brian d foy)
+
+Ctags uses an index to quickly find things in source code, and many
+popular editors support ctags for several different languages,
+including Perl.
-There is also a simple one at
-http://www.cpan.org/authors/id/TOMC/scripts/ptags.gz which may do
-the trick. It can be easy to hack this into what you want.
+Exuberant ctags supports Perl: http://ctags.sourceforge.net/
+
+You might also try pltags: http://www.mscha.com/pltags.zip
=head2 Is there an IDE or Windows Perl Editor?
Perl programs are just plain text, so any editor will do.
-If you're on Unix, you already have an IDE--Unix itself. The UNIX
+If you're on Unix, you already have an IDE--Unix itself. The Unix
philosophy is the philosophy of several small tools that each do one
thing and do it well. It's like a carpenter's toolbox.
=item Eclipse
-The Eclipse Perl Integration Project integrates Perl
+http://e-p-i-c.sf.net/
+
+The Eclipse Perl Integration Project integrates Perl
editing/debugging with Eclipse.
-The website for the project is http://e-p-i-c.sf.net/
+=item Enginsite
+
+http://www.enginsite.com/
+
+Perl Editor by EngInSite is a complete integrated development
+environment (IDE) for creating, testing, and debugging Perl scripts;
+the tool runs on Windows 9x/NT/2000/XP or later.
=item Komodo
+http://www.ActiveState.com/Products/Komodo/
+
ActiveState's cross-platform (as of October 2004, that's Windows, Linux,
and Solaris), multi-language IDE has Perl support, including a regular expression
-debugger and remote debugging
-( http://www.ActiveState.com/Products/Komodo/ ).
+debugger and remote debugging.
+
+=item Notepad++
+
+http://notepad-plus.sourceforge.net/
=item Open Perl IDE
-( http://open-perl-ide.sourceforge.net/ )
+http://open-perl-ide.sourceforge.net/
+
Open Perl IDE is an integrated development environment for writing
and debugging Perl scripts with ActiveState's ActivePerl distribution
under Windows 95/98/NT/2000.
=item OptiPerl
-( http://www.optiperl.com/ ) is a Windows IDE with simulated CGI
-environment, including debugger and syntax highlighting editor.
+http://www.optiperl.com/
+
+OptiPerl is a Windows IDE with simulated CGI environment, including
+debugger and syntax-highlighting editor.
+
+=item Padre
+
+http://padre.perlide.org/
+
+Padre is cross-platform IDE for Perl written in Perl using wxWidgets to provide
+a native look and feel. It's open source under the Artistic License.
=item PerlBuilder
-( http://www.solutionsoft.com/perl.htm ) is an integrated development
-environment for Windows that supports Perl development.
+http://www.solutionsoft.com/perl.htm
+
+PerlBuilder is an integrated development environment for Windows that
+supports Perl development.
=item visiPerl+
-( http://helpconsulting.net/visiperl/ )
+http://helpconsulting.net/visiperl/
+
From Help Consulting, for Windows.
=item Visual Perl
-( http://www.activestate.com/Products/Visual_Perl/ )
+http://www.activestate.com/Products/Visual_Perl/
+
Visual Perl is a Visual Studio.NET plug-in from ActiveState.
+=item Zeus
+
+http://www.zeusedit.com/lookmain.html
+
+Zeus for Window is another Win32 multi-language editor/IDE
+that comes with support for Perl.
=back
-For editors: if you're on Unix you probably have vi or a vi clone already,
-and possibly an emacs too, so you may not need to download anything.
-In any emacs the cperl-mode (M-x cperl-mode) gives you perhaps the
-best available Perl editing mode in any editor.
-
-If you are using Windows, you can use any editor that lets
-you work with plain text, such as NotePad or WordPad. Word
-processors, such as Microsoft Word or WordPerfect, typically
-do not work since they insert all sorts of behind-the-scenes
-information, although some allow you to save files as "Text
-Only". You can also download text editors designed
-specifically for programming, such as Textpad
-( http://www.textpad.com/ ) and UltraEdit
-( http://www.ultraedit.com/ ), among others.
-
-If you are using MacOS, the same concerns apply. MacPerl
-(for Classic environments) comes with a simple editor.
-Popular external editors are BBEdit ( http://www.bbedit.com/ )
-or Alpha ( http://www.his.com/~jguyer/Alpha/Alpha8.html ). MacOS X users can
-use Unix editors as well.
+For editors: if you're on Unix you probably have vi or a vi clone
+already, and possibly an emacs too, so you may not need to download
+anything. In any emacs the cperl-mode (M-x cperl-mode) gives you
+perhaps the best available Perl editing mode in any editor.
+
+If you are using Windows, you can use any editor that lets you work
+with plain text, such as NotePad or WordPad. Word processors, such as
+Microsoft Word or WordPerfect, typically do not work since they insert
+all sorts of behind-the-scenes information, although some allow you to
+save files as "Text Only". You can also download text editors designed
+specifically for programming, such as Textpad (
+http://www.textpad.com/ ) and UltraEdit ( http://www.ultraedit.com/ ),
+among others.
+
+If you are using MacOS, the same concerns apply. MacPerl (for Classic
+environments) comes with a simple editor. Popular external editors are
+BBEdit ( http://www.bbedit.com/ ) or Alpha (
+http://www.his.com/~jguyer/Alpha/Alpha8.html ). MacOS X users can use
+Unix editors as well.
=over 4
nvi ( http://www.bostic.com/vi/ , available from CPAN in src/misc/) is
yet another vi clone, unfortunately not available for Windows, but in
-UNIX platforms you might be interested in trying it out, firstly because
+Unix platforms you might be interested in trying it out, firstly because
strictly speaking it is not a vi clone, it is the real vi, or the new
incarnation of it, and secondly because you can embed Perl inside it
to use Perl as the scripting language. nvi is not alone in this,
though: at least also vim and vile offer an embedded Perl.
-The following are Win32 multilanguage editor/IDESs that support Perl:
+The following are Win32 multilanguage editor/IDEs that support Perl:
=over 4
http://www.slickedit.com/
+=item ConTEXT
+
+http://www.contexteditor.org/
+
=back
There is also a toyedit Text widget based editor written in Perl
that is distributed with the Tk module on CPAN. The ptkdb
-( http://world.std.com/~aep/ptkdb/ ) is a Perl/tk based debugger that
+( http://ptkdb.sourceforge.net/ ) is a Perl/Tk-based debugger that
acts as a development environment of sorts. Perl Composer
( http://perlcomposer.sourceforge.net/ ) is an IDE for Perl/Tk
GUI creation.
=item Ksh
-from the MKS Toolkit ( http://www.mks.com/ ), or the Bourne shell of
+from the MKS Toolkit ( http://www.mkssoftware.com/ ), or the Bourne shell of
the U/WIN environment ( http://www.research.att.com/sw/tools/uwin/ )
=item Tcsh
=item Zsh
-ftp://ftp.blarg.net/users/amol/zsh/ , see also http://www.zsh.org/
+http://www.zsh.org/
=back
MKS and U/WIN are commercial (U/WIN is free for educational and
-research purposes), Cygwin is covered by the GNU Public License (but
-that shouldn't matter for Perl use). The Cygwin, MKS, and U/WIN all
-contain (in addition to the shells) a comprehensive set of standard
-UNIX toolkit utilities.
+research purposes), Cygwin is covered by the GNU General Public
+License (but that shouldn't matter for Perl use). The Cygwin, MKS,
+and U/WIN all contain (in addition to the shells) a comprehensive set
+of standard Unix toolkit utilities.
If you're transferring text files between Unix and Windows using FTP
be sure to transfer them in ASCII mode so the ends of lines are
=item Affrus
-is a full Perl development enivornment with full debugger support
+is a full Perl development environment with full debugger support
( http://www.latenightsw.com ).
=item Alpha
is an editor, written and extensible in Tcl, that nonetheless has
-built in support for several popular markup and programming languages
+built-in support for several popular markup and programming languages,
including Perl and HTML ( http://www.his.com/~jguyer/Alpha/Alpha8.html ).
=item BBEdit and BBEdit Lite
are text editors for Mac OS that have a Perl sensitivity mode
( http://web.barebones.com/ ).
-
=back
-Pepper and Pe are programming language sensitive text editors for Mac
-OS X and BeOS respectively ( http://www.hekkelman.com/ ).
-
=head2 Where can I get Perl macros for vi?
For a complete version of Tom Christiansen's vi configuration file,
the current version of vi out of Berkeley, which incidentally can be built
with an embedded Perl interpreter--see http://www.cpan.org/src/misc/ .
-=head2 Where can I get perl-mode for emacs?
+=head2 Where can I get perl-mode or cperl-mode for emacs?
+X<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
come with the standard Emacs 19 distribution.
-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.
-
Note that the perl-mode of emacs will have fits with C<"main'foo">
(single quote), and mess up the indentation and highlighting. You
are probably using C<"main::foo"> in new Perl code anyway, so this
shouldn't be an issue.
+For CPerlMode, see http://www.emacswiki.org/cgi-bin/wiki/CPerlMode
+
=head2 How can I use curses with Perl?
The Curses module from CPAN provides a dynamically loadable object
this program repeats a command and updates the screen as needed, rendering
B<rep ps axu> similar to B<top>.
-=head2 How can I use X or Tk with Perl?
+=head2 How can I write a GUI (X, Tk, Gtk, etc.) in Perl?
+X<GUI> X<Tk> X<Wx> X<WxWidgets> X<Gtk> X<Gtk2> X<CamelBones> X<Qt>
+
+(contributed by Ben Morrow)
+
+There are a number of modules which let you write GUIs in Perl. Most
+GUI toolkits have a perl interface: an incomplete list follows.
+
+=over 4
+
+=item Tk
+
+This works under Unix and Windows, and the current version doesn't
+look half as bad under Windows as it used to. Some of the gui elements
+still don't 'feel' quite right, though. The interface is very natural
+and 'perlish', making it easy to use in small scripts that just need a
+simple gui. It hasn't been updated in a while.
+
+=item Wx
+
+This is a Perl binding for the cross-platform wxWidgets toolkit
+( http://www.wxwidgets.org ). It works under Unix, Win32 and Mac OS X,
+using native widgets (Gtk under Unix). The interface follows the C++
+interface closely, but the documentation is a little sparse for someone
+who doesn't know the library, mostly just referring you to the C++
+documentation.
+
+=item Gtk and Gtk2
+
+These are Perl bindings for the Gtk toolkit ( http://www.gtk.org ). The
+interface changed significantly between versions 1 and 2 so they have
+separate Perl modules. It runs under Unix, Win32 and Mac OS X (currently
+it requires an X server on Mac OS, but a 'native' port is underway), and
+the widgets look the same on every platform: i.e., they don't match the
+native widgets. As with Wx, the Perl bindings follow the C API closely,
+and the documentation requires you to read the C documentation to
+understand it.
+
+=item Win32::GUI
+
+This provides access to most of the Win32 GUI widgets from Perl.
+Obviously, it only runs under Win32, and uses native widgets. The Perl
+interface doesn't really follow the C interface: it's been made more
+Perlish, and the documentation is pretty good. More advanced stuff may
+require familiarity with the C Win32 APIs, or reference to MSDN.
-Tk is a completely Perl-based, object-oriented interface to the Tk toolkit
-that doesn't force you to use Tcl just to get at Tk. Sx is an interface
-to the Athena Widget set. Both are available from CPAN. See the
-directory http://www.cpan.org/modules/by-category/08_User_Interfaces/
+=item CamelBones
-Invaluable for Perl/Tk programming are the Perl/Tk FAQ at
-http://phaseit.net/claird/comp.lang.perl.tk/ptkFAQ.html , the Perl/Tk Reference
-Guide available at
-http://www.cpan.org/authors/Stephen_O_Lidie/ , and the
-online manpages at
-http://www-users.cs.umn.edu/%7Eamundson/perl/perltk/toc.html .
+CamelBones ( http://camelbones.sourceforge.net ) is a Perl interface to
+Mac OS X's Cocoa GUI toolkit, and as such can be used to produce native
+GUIs on Mac OS X. It's not on CPAN, as it requires frameworks that
+CPAN.pm doesn't know how to install, but installation is via the
+standard OSX package installer. The Perl API is, again, very close to
+the ObjC API it's wrapping, and the documentation just tells you how to
+translate from one to the other.
+
+=item Qt
+
+There is a Perl interface to TrollTech's Qt toolkit, but it does not
+appear to be maintained.
+
+=item Athena
+
+Sx is an interface to the Athena widget set which comes with X, but
+again it appears not to be much used nowadays.
+
+=back
=head2 How can I make my Perl program run faster?
and profile to make sure you're optimizing the right part, look for
better algorithms instead of microtuning your code, and when all else
fails consider just buying faster hardware. You will probably want to
-read the answer to the earlier question ``How do I profile my Perl
-programs?'' if you haven't done so already.
+read the answer to the earlier question "How do I profile my Perl
+programs?" if you haven't done so already.
A different approach is to autoload seldom-used Perl code. See the
AutoSplit and AutoLoader modules in the standard distribution for
Ditto for stringifying large arrays:
- {
- local $, = "\n";
- print @big_array;
- }
+ {
+ local $, = "\n";
+ print @big_array;
+ }
is much more memory-efficient than either
- print join "\n", @big_array;
+ print join "\n", @big_array;
or
- {
- local $" = "\n";
- print "@big_array";
- }
+ {
+ local $" = "\n";
+ print "@big_array";
+ }
=item * Pass by reference
Pass arrays and hashes by reference, not by value. For one thing, it's
the only way to pass multiple lists or hashes (or both) in a single
call/return. It also avoids creating a copy of all the contents. This
-requires some judgment, however, because any changes will be propagated
+requires some judgement, however, because any changes will be propagated
back to the original data. If you really want to mangle (er, modify) a
copy, you'll have to sacrifice the memory needed to make one.
-=item * Tie large variables to disk.
+=item * Tie large variables to disk
For "big" data stores (i.e. ones that exceed available memory) consider
using one of the DB modules to store it on disk instead of in RAM. This
cannot be reclaimed or reused even if they go out of scope. It is
reserved in case the variables come back into scope. Memory allocated
to global variables can be reused (within your program) by using
-undef()ing and/or delete().
+undef() and/or delete().
On most operating systems, memory allocated to a program can never be
returned to the system. That's why long-running programs sometimes re-
and on the way you write your CGI programs, so investigate them with
care.
-See http://www.cpan.org/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/velocigen/ )
-might also be worth looking at. It will allow you to increase the
-performance of your Perl programs, running programs up to 25 times
-faster than normal CGI Perl when 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.
+See also
+http://www.cpan.org/modules/by-category/15_World_Wide_Web_HTML_HTTP_CGI/ .
=head2 How can I hide the source for my Perl program?
Delete it. :-) Seriously, there are a number of (mostly
-unsatisfactory) solutions with varying levels of ``security''.
+unsatisfactory) solutions with varying levels of "security".
First of all, however, you I<can't> take away read permission, because
the source code has to be readable in order to be compiled and
5.8 the Filter::Simple and Filter::Util::Call modules are included in
the standard distribution), but any decent programmer will be able to
decrypt it. You can try using the byte code compiler and interpreter
-described below, but the curious might still be able to de-compile it.
-You can try using the native-code compiler described below, but
-crackers might be able to disassemble it. These pose varying degrees
-of difficulty to people wanting to get at your code, but none can
-definitively conceal it (true of every language, not just Perl).
+described later in L<perlfaq3>, but the curious might still be able to
+de-compile it. You can try using the native-code compiler described
+later, but crackers might be able to disassemble it. These pose
+varying degrees of difficulty to people wanting to get at your code,
+but none can definitively conceal it (true of every language, not just
+Perl).
It is very easy to recover the source of Perl programs. You simply
feed the program to the perl interpreter and use the modules in
If you're concerned about people profiting from your code, then the
bottom line is that nothing but a restrictive license will give you
legal security. License your software and pepper it with threatening
-statements like ``This is unpublished proprietary software of XYZ Corp.
+statements like "This is unpublished proprietary software of XYZ Corp.
Your access to it does not give you permission to use it blah blah
-blah.'' We are not lawyers, of course, so you should see a lawyer if
+blah." We are not lawyers, of course, so you should see a lawyer if
you want to be sure your license's wording will stand up in court.
=head2 How can I compile my Perl program into byte code or C?
In general, you can't do this. There are some things that may work
for your situation though. People usually ask this question
-because they want to distribute their works without giving away
+because they want to distribute their works without giving away
the source code, and most solutions trade disk space for convenience.
You probably won't see much of a speed increase either, since most
-solutions simply bundle a Perl interpreter in the final product
+solutions simply bundle a Perl interpreter in the final product
(but see L<How can I make my Perl program run faster?>).
-The Perl Archive Toolkit (http://par.perl.org/index.cgi) is
-Perl's analog to Java's JAR. It's freely available and on
-CPAN (http://search.cpan.org/dist/PAR/).
-
-The B::* namespace, often called "the Perl compiler", but is really a
-way for Perl programs to peek at its innards rather than create
-pre-compiled versions of your program. However. the B::Bytecode
-module can turn your script into a bytecode format that could be
-loaded later by the ByteLoader module and executed as a regular Perl
-script.
+The Perl Archive Toolkit ( http://par.perl.org/ ) is Perl's
+analog to Java's JAR. It's freely available and on CPAN (
+http://search.cpan.org/dist/PAR/ ).
-There are also some commercial products that may work for
-you, although you have to buy a license for them.
+There are also some commercial products that may work for you, although
+you have to buy a license for them.
-The Perl Dev Kit
-(http://www.activestate.com/Products/Perl_Dev_Kit/) from
-ActiveState can "Turn your Perl programs into ready-to-run
+The Perl Dev Kit ( http://www.activestate.com/Products/Perl_Dev_Kit/ )
+from ActiveState can "Turn your Perl programs into ready-to-run
executables for HP-UX, Linux, Solaris and Windows."
-Perl2Exe (http://www.indigostar.com/perl2exe.htm) is a
-command line program for converting perl scripts to
-executable files. It targets both Windows and unix
-platforms.
-
-
-=head2 How can I compile Perl into Java?
-
-You can also integrate Java and Perl with the
-Perl Resource Kit from O'Reilly Media. See
-http://www.oreilly.com/catalog/prkunix/ .
-
-Perl 5.6 comes with Java Perl Lingo, or JPL. JPL, still in
-development, allows Perl code to be called from Java. See jpl/README
-in the Perl source tree.
+Perl2Exe ( http://www.indigostar.com/perl2exe.htm ) is a command line
+program for converting perl scripts to executable files. It targets both
+Windows and Unix platforms.
=head2 How can I get C<#!perl> to work on [MS-DOS,NT,...]?
extproc perl -S -your_switches
as the first line in C<*.cmd> file (C<-S> due to a bug in cmd.exe's
-`extproc' handling). For DOS one should first invent a corresponding
+"extproc" handling). For DOS one should first invent a corresponding
batch file and codify it in C<ALTERNATE_SHEBANG> (see the
F<dosish.h> file in the source distribution for more information).
For example:
- # Unix
+ # Unix (including Mac OS X)
perl -e 'print "Hello world\n"'
# DOS, etc.
perl -e "print \"Hello world\n\""
- # Mac
+ # Mac Classic
print "Hello world\n"
(then Run "Myscript" or Shift-Command-R)
For modules, get the CGI or LWP modules from CPAN. For textbooks,
see the two especially dedicated to web stuff in the question on
-books. For problems and questions related to the web, like ``Why
-do I get 500 Errors'' or ``Why doesn't it run from the browser right
-when it runs fine on the command line'', see the troubleshooting
+books. For problems and questions related to the web, like "Why
+do I get 500 Errors" or "Why doesn't it run from the browser right
+when it runs fine on the command line", see the troubleshooting
guides and references in L<perlfaq9> or in the CGI MetaFAQ:
http://www.perl.org/CGI_MetaFAQ.html
A good place to start is L<perltoot>, and you can use L<perlobj>,
L<perlboot>, L<perltoot>, L<perltooc>, and L<perlbot> for reference.
-(If you are using really old Perl, you may not have all of these,
-try http://www.perldoc.com/ , but consider upgrading your perl.)
A good book on OO on Perl is the "Object-Oriented Perl"
-by Damian Conway from Manning Publications,
-http://www.manning.com/Conway/index.html
+by Damian Conway from Manning Publications, or "Intermediate Perl"
+by Randal Schwartz, brian d foy, and Tom Phoenix from O'Reilly Media.
-=head2 Where can I learn about linking C with Perl? [h2xs, xsubpp]
+=head2 Where can I learn about linking C with Perl?
If you want to call C from Perl, start with L<perlxstut>,
moving on to L<perlxs>, L<xsubpp>, and L<perlguts>. If you want to
how the authors of existing extension modules wrote their code and
solved their problems.
+You might not need all the power of XS. The Inline::C module lets
+you put C code directly in your Perl source. It handles all the
+magic to make it work. You still have to learn at least some of
+the perl API but you won't have to deal with the complexity of the
+XS support files.
+
=head2 I've read perlembed, perlguts, etc., but I can't embed perl in my C program; what am I doing wrong?
Download the ExtUtils::Embed kit from CPAN and run `make test'. If
=head2 What's MakeMaker?
-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>.
+(contributed by brian d foy)
+
+The C<ExtUtils::MakeMaker> module, better known simply as "MakeMaker",
+turns a Perl script, typically called C<Makefile.PL>, into a Makefile.
+The Unix tool C<make> uses this file to manage dependencies and actions
+to process and install a Perl distribution.
=head1 AUTHOR AND COPYRIGHT
-Copyright (c) 1997-2005 Tom Christiansen, Nathan Torkington, and
+Copyright (c) 1997-2010 Tom Christiansen, Nathan Torkington, and
other authors as noted. All rights reserved.
This documentation is free; you can redistribute it and/or modify it
https://perl5.git.perl.org / perl5.git / blobdiff