=head1 NAME
-perlfaq3 - Programming Tools ($Revision: 1.38 $, $Date: 1999/05/23 16:08:30 $)
+perlfaq3 - Programming Tools
=head1 DESCRIPTION
Have you looked at CPAN (see L<perlfaq2>)? The chances are that
someone has already written a module that can solve your problem.
-Have you read the appropriate man pages? Here's a brief index:
+Have you read the appropriate manpages? Here's a brief index:
Basics perldata, perlvar, perlsyn, perlop, perlsub
Execution perlrun, perldebug
Regexes perlre, perlfunc, perlop, perllocale
Moving to perl5 perltrap, perl
Linking w/C perlxstut, perlxs, perlcall, perlguts, perlembed
- Various http://www.perl.com/CPAN/doc/FMTEYEWTK/index.html
- (not a man-page but still useful)
+ Various http://www.cpan.org/misc/olddoc/FMTEYEWTK.tgz
+ (not a man-page but still useful, a collection
+ of various essays on Perl techniques)
-A crude table of contents for the Perl man
page set is found in L<perltoc>.
+A crude table of contents for the Perl manpage set is found in L<perltoc>.
=head2 How can I use Perl interactively?
The typical approach uses the Perl debugger, described in the
-perldebug(1) man page, on an ``empty'' program, like this:
+perldebug(1) manpage, on an "empty" program, like this:
perl -de 42
=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
-commands. perlsh from the source distribution is simplistic and
-uninteresting, but may still be what you want.
+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://sourceforge.net/projects/psh/ .
-=head2 How do I debug my Perl programs?
+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://pardus-larus.student.utwente.nl/~pardus/projects/zoidberg/
+or your local CPAN mirror.
-Have you used C<-w>? It enables warnings for dubious practices.
+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.
-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> or C<our> or C<use vars>.
+=head2 How do I find which modules are installed on my system?
-Did you check the returns of each and every system call? The operating
-system (and thus Perl) tells you whether they worked or not, and if not
-why.
+From the command line, you can use the C<cpan> command's C<-l> switch:
- open(FH, "> /etc/cantwrite")
- or die "Couldn't write to /etc/cantwrite: $!\n";
+ $ cpan -l
-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>.
+You can also use C<cpan>'s C<-a> switch to create an autobundle file
+that C<CPAN.pm> understands and cna use to re-install every module:
-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.
+ $ cpan -a
-=head2 How do I profile my Perl programs?
+Inside a Perl program, 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).
-You should get the Devel::DProf module from CPAN, and also use
-Benchmark.pm from the standard distribution. Benchmark lets you time
-specific portions of your code, while Devel::DProf gives detailed
-breakdowns of where your code spends its time.
+ use ExtUtils::Installed;
-Here's a sample use of Benchmark:
+ my $inst = ExtUtils::Installed->new();
+ my @modules = $inst->modules();
- use Benchmark;
+If you want a list of all of the Perl module filenames, you
+can use File::Find::Rule.
- @junk = `cat /etc/motd`;
- $count = 10_000;
+ use File::Find::Rule;
- timethese($count, {
- 'map' => sub { my @a = @junk;
- map { s/a/b/ } @a;
- return @a
- },
- 'for' => sub { my @a = @junk;
- local $_;
- for (@a) { s/a/b/ };
- return @a },
- });
+ my @files = File::Find::Rule->
+ extras({follow => 1})->
+ file()->
+ name( '*.pm' )->
+ in( @INC )
+ ;
-This is what it prints (on one machine--your results will be dependent
-on your hardware, operating system, and the load on your machine):
+If you do not have that module, you can do the same thing
+with File::Find which is part of the standard library.
- 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)
+ use File::Find;
+ my @files;
-Be aware that a good benchmark is very hard to write. It only tests the
-data you give it, and really proves little about differing complexities
-of contrasting algorithms.
+ find(
+ {
+ wanted => sub {
+ push @files, $File::Find::fullname
+ if -f $File::Find::fullname && /\.pm$/
+ },
+ follow => 1,
+ follow_skip => 2,
+ },
+ @INC
+ );
-=head2 How do I cross-reference my Perl programs?
+ print join "\n", @files;
-The B::Xref module, shipped with the new, alpha-release Perl compiler
-(not the general distribution prior to the 5.005 release), can be used
-to generate cross-reference reports for Perl programs.
+If you simply need to quickly check 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).
- perl -MO=Xref[,OPTIONS] scriptname.plx
+ $ perldoc Module::Name
-=head2 Is there a pretty-printer (formatter) for Perl?
+You can also try to include the module in a one-liner to see if
+perl finds it.
-There is no program that will reformat Perl as much as indent(1) does
-for C. The complex feedback between the scanner and the parser (this
-feedback is what confuses the vgrind and emacs programs) makes it
-challenging at best to write a stand-alone Perl parser.
+ $ perl -MModule::Name -e1
-Of course, if you simply follow the guidelines in L<perlstyle>, you
-shouldn't need to reformat. The habit of formatting your code as you
-write it will help prevent bugs. Your editor can and should help you
-with this. The perl-mode for emacs can provide a remarkable amount of
-help with most (but not all) code, and even less programmable editors
-can provide significant assistance. Tom swears by the following
-settings in vi and its clones:
+=head2 How do I debug my Perl programs?
- set ai sw=4
- map! ^O {^M}^[O^T
+(contributed by brian d foy)
-Now 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. If you haven't used the last one, you're missing
-a lot. A more complete example, with comments, can be found at
-http://www.perl.com/CPAN-local/authors/id/TOMC/scripts/toms.exrc.gz
+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>.
-If you are used to using the I<vgrind> program for printing out nice code
-to a laser printer, you can take a stab at this using
-http://www.perl.com/CPAN/doc/misc/tips/working.vgrind.entry, but the
-results are not particularly satisfying for sophisticated code.
+ #!/usr/bin/perl
+ use strict;
+ use warnings;
-The a2ps at http://www.infres.enst.fr/%7Edemaille/a2ps/ does lots of things
-related to generating nicely printed output of documents.
+Beyond that, the simplest debugger is the C<print> function. Use it
+to look at values as you run your program:
-=head2 Is there a ctags for Perl?
+ print STDERR "The value is [$value]\n";
-There's a simple one at
-http://www.perl.com/CPAN/authors/id/TOMC/scripts/ptags.gz which may do
-the trick. And if not, it's easy to hack into what you want.
+The C<Data::Dumper> module can pretty-print Perl data structures:
-=head2 Is there an IDE or Windows Perl Editor?
+ use Data::Dumper qw( Dumper );
+ print STDERR "The hash is " . Dumper( \%hash ) . "\n";
+
+Perl comes with an interactive debugger, which you can start with the
+C<-d> switch. It's fully explained in L<perldebug>.
+
+If you'd like a graphical user interface and you have 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 Devel::ebug (which you can call with the -D switch as -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?
+
+(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
-If you're on Unix, you already have an IDE -- Unix itself. This powerful
-IDE derives from its interoperability, flexibility, and configurability.
-If you really want to get a feel for Unix-qua-IDE, the best thing to do
-is to find some high-powered programmer whose native language is Unix.
-Find someone who has been at this for many years, and just sit back
-and watch them at work. They have created their own IDE, one that
-suits their own tastes and aptitudes. Quietly observe them edit files,
-move them around, compile them, debug them, test them, etc. The entire
-development *is* integrated, like a top-of-the-line German sports car:
-functional, powerful, and elegant. You will be absolutely astonished
-at the speed and ease exhibited by the native speaker of Unix in his
-home territory. The art and skill of a virtuoso can only be seen to be
-believed. That is the path to mastery -- all these cobbled little IDEs
-are expensive toys designed to sell a flashy demo using cheap tricks,
-and being optimized for immediate but shallow understanding rather than
-enduring use, are but a dim palimpsest of real tools.
-
-In short, you just have to learn the toolbox. However, if you're not
-on Unix, then your vendor probably didn't bother to provide you with
-a proper toolbox on the so-called complete system that you forked out
-your hard-earned cash on.
-
-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/%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 macros for vi?
-
-For a complete version of Tom Christiansen's vi configuration file,
-see http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/toms.exrc.gz,
-the standard benchmark file for vi emulators. This runs best with nvi,
-the current version of vi out of Berkeley, which incidentally can be built
-with an embedded Perl interpreter -- see http://www.perl.com/CPAN/src/misc.
-
-=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
-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.
-
-=head2 How can I use curses with Perl?
-
-The Curses module from CPAN provides a dynamically loadable object
-module interface to a curses library. A small demo can be found at the
-directory http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/rep;
-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?
-
-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.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/%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/%7Eamundson/perl/perltk/toc.html .
-
-=head2 How can I generate simple menus without using CGI or Tk?
-
-The http://www.perl.com/CPAN/authors/id/SKUNZ/perlmenu.v4.0.tar.gz
-module, which is curses-based, can help with this.
-
-=head2 What is undump?
-
-See the next questions.
-
-=head2 How can I make my Perl program run faster?
-
-The best way to do this is to come up with a better algorithm. This
-can often make a dramatic difference. Chapter 8 in the Camel has some
-efficiency tips in it you might want to look at. Jon Bentley's book
-``Programming Pearls'' (that's not a misspelling!) has some good tips
-on optimization, too. Advice on benchmarking boils down to: benchmark
-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.
-
-A different approach is to autoload seldom-used Perl code. See the
-AutoSplit and AutoLoader modules in the standard distribution for
-that. Or you could locate the bottleneck and think about writing just
-that part in C, the way we used to take bottlenecks in C code and
-write them in assembler. Similar to rewriting in C is the use of
-modules that have critical sections written in C (for instance, the
-PDL module from CPAN).
-
-In some cases, it may be worth it to use the backend compiler to
-produce byte code (saving compilation time) or compile into C, which
-will certainly save compilation time and sometimes a small amount (but
-not much) execution time. See the question about compiling your Perl
-programs for more on the compiler--the wins aren't as obvious as you'd
-hope.
-
-If you're currently linking your perl executable to a shared I<libc.so>,
-you can often gain a 10-25% performance benefit by rebuilding it to
-link with a static libc.a instead. This will make a bigger perl
-executable, but your Perl programs (and programmers) may thank you for
-it. See the F<INSTALL> file in the source distribution for more
-information.
-
-Unsubstantiated reports allege that Perl interpreters that use sfio
-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 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
-a viable option, as it only worked on a few architectures, and
-wasn't a good solution anyway.
-
-=head2 How can I make my Perl program take less memory?
-
-When it comes to time-space tradeoffs, Perl nearly always prefers to
-throw memory at a problem. Scalars in Perl use more memory than
-strings in C, arrays take more than that, and hashes use even more. While
-there's still a lot to be done, recent releases have been addressing
-these issues. For example, as of 5.004, duplicate hash keys are
-shared amongst all hashes using them, so require no reallocation.
-
-In some cases, using substr() or vec() to simulate arrays can be
-highly beneficial. For example, an array of a thousand booleans will
-take at least 20,000 bytes of space, but it can be turned into one
-125-byte bit vector for a considerable memory savings. The standard
-Tie::SubstrHash module can also help for certain types of data
-structure. If you're working with specialist data structures
-(matrices, for instance) modules that implement these in C may use
-less memory than equivalent Perl modules.
-
-Another thing to try is learning whether your Perl was compiled with
-the system malloc or with Perl's builtin malloc. Whichever one it
-is, try using the other one and see whether this makes a difference.
-Information about malloc is in the F<INSTALL> file in the source
-distribution. You can find out whether you are using perl's malloc by
-typing C<perl -V:usemymalloc>.
-
-=head2 Is it unsafe to return a pointer to local data?
-
-No, Perl's garbage collection system takes care of this.
-
- sub makeone {
- my @a = ( 1 .. 10 );
- return \@a;
- }
-
- for $i ( 1 .. 10 ) {
- push @many, makeone();
- }
-
- print $many[4][5], "\n";
-
- print "@many\n";
-
-=head2 How can I free an array or hash so my program shrinks?
-
-You can't. On most operating systems, memory allocated to a program
-can never be returned to the system. That's why long-running programs
-sometimes re-exec themselves. Some operating systems (notably,
-FreeBSD and Linux) allegedly reclaim large chunks of memory that is no
-longer used, but it doesn't appear to happen with Perl (yet). The Mac
-appears to be the only platform that will reliably (albeit, slowly)
-return memory to the OS.
-
-We've had reports that on Linux (Redhat 5.1) on Intel, C<undef
-$scalar> will return memory to the system, while on Solaris 2.6 it
-won't. In general, try it yourself and see.
-
-However, judicious use of my() on your variables will help make sure
-that they go out of scope so that Perl can free up their storage for
-use in other parts of your program. A global variable, of course, never
-goes out of scope, so you can't get its space automatically reclaimed,
-although undef()ing and/or delete()ing it will achieve the same effect.
-In general, memory allocation and de-allocation isn't something you can
-or should be worrying about much in Perl, but even this capability
-(preallocation of data types) is in the works.
-
-=head2 How can I make my CGI script more efficient?
-
-Beyond the normal measures described to make general Perl programs
-faster or smaller, a CGI program has additional issues. It may be run
-several times per second. Given that each time it runs it will need
-to be re-compiled and will often allocate a megabyte or more of system
-memory, this can be a killer. Compiling into C B<isn't going to help
-you> because the process start-up overhead is where the bottleneck is.
-
-There are two popular ways to avoid this overhead. One solution
-involves running the Apache HTTP server (available from
-http://www.apache.org/) with either of the mod_perl or mod_fastcgi
-plugin modules.
-
-With mod_perl and the Apache::Registry module (distributed with
-mod_perl), httpd will run with an embedded Perl interpreter which
-pre-compiles your script and then executes it within the same address
-space without forking. The Apache extension also gives Perl access to
-the internal server API, so modules written in Perl can do just about
-anything a module written in C can. For more on mod_perl, see
-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
-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 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 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?
-
-Delete it. :-) Seriously, there are a number of (mostly
-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
-interpreted. (That doesn't mean that a CGI script's source is
-readable by people on the web, though, only by people with access to
-the filesystem) So you have to leave the permissions at the socially
-friendly 0755 level.
-
-Some people regard this as a security problem. If your program does
-insecure things, and relies on people not knowing how to exploit those
-insecurities, it is not secure. It is often possible for someone to
-determine the insecure things and exploit them without viewing the
-source. Security through obscurity, the name for hiding your bugs
-instead of fixing them, is little security indeed.
-
-You can try using encryption via source filters (Filter::* from CPAN),
-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 (this is true of every
-language, not just Perl).
-
-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.
-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
-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?
-
-Malcolm Beattie has written a multifunction backend compiler,
-available from CPAN, that can do both these things. It is included
-in the perl5.005 release, but is still considered experimental.
-This means it's fun to play with if you're a programmer but not
-really for people looking for turn-key solutions.
-
-Merely compiling into C does not in and of itself guarantee that your
-code will run very much faster. That's because except for lucky cases
-where a lot of native type inferencing is possible, the normal Perl
-run time system is still present and so your program will take just as
-long to run and be just as big. Most programs save little more than
-compilation time, leaving execution no more than 10-30% faster. A few
-rare programs actually benefit significantly (like several times
-faster), but this takes some tweaking of your code.
-
-You'll probably be astonished to learn that the current version of the
-compiler generates a compiled form of your script whose executable is
-just as big as the original perl executable, and then some. That's
-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
-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!
-
-In general, the compiler will do nothing to make a Perl program smaller,
-faster, more portable, or more secure. In fact, it will usually hurt
-all of those. The executable will be bigger, your VM system may take
-longer to load the whole thing, the binary is fragile and hard to fix,
-and compilation never stopped software piracy in the form of crackers,
-viruses, or bootleggers. The real advantage of the compiler is merely
-packaging, and once you see the size of what it makes (well, unless
-you use a shared I<libperl.so>), you'll probably want a complete
-Perl install anyway.
-
-=head2 How can I compile Perl into Java?
-
-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 5.6 release
-of Perl.
-
-=head2 How can I get C<#!perl> to work on [MS-DOS,NT,...]?
-
-For OS/2 just use
-
- 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
-batch file, and codify it in C<ALTERNATIVE_SHEBANG> (see the
-F<INSTALL> file in the source distribution for more information).
-
-The Win95/NT installation, when using the ActiveState port of Perl,
-will modify the Registry to associate the C<.pl> extension with the
-perl interpreter. If you install another port, perhaps even building
-your own Win95/NT Perl from the standard sources by using a Windows port
-of gcc (e.g., with cygwin32 or mingw32), then you'll have to modify
-the Registry yourself. In addition to associating C<.pl> with the
-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 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 programs working for a web server. This is an EXTREMELY big
-security risk. Take the time to figure out how to do it correctly.
+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>.
-=head2 Can I write useful Perl programs on the command line?
+ dprofpp
-Yes. Read L<perlrun> for more information. Some examples follow.
-(These assume standard Unix shell quoting rules.)
+You can also do the profiling and reporting in one step with the C<-p>
+switch to <dprofpp>:
- # sum first and last fields
- perl -lane 'print $F[0] + $F[-1]' *
+ dprofpp -p program.pl
- # identify text files
- perl -le 'for(@ARGV) {print if -f && -T _}' *
+The C<Devel::NYTProf> (New York Times Profiler) does both statement
+and subroutine profiling. It's available from CPAN and you also invoke
+it with the C<-d> switch:
- # remove (most) comments from C program
- perl -0777 -pe 's{/\*.*?\*/}{}gs' foo.c
+ perl -d:NYTProf some_perl.pl
- # make file a month younger than today, defeating reaper daemons
- perl -e '$X=24*60*60; utime(time(),time() + 30 * $X,@ARGV)' *
+Like C<DProf>, it creates a database of the profile information that you
+can turn into reports. The C<nytprofhtml> command turns the data into
+an HTML report similar to the C<Devel::Cover> report:
- # find first unused uid
- perl -le '$i++ while getpwuid($i); print $i'
+ nytprofhtml
- # display reasonable manpath
- echo $PATH | perl -nl -072 -e '
- s![^/+]*$!man!&&-d&&!$s{$_}++&&push@m,$_;END{print"@m"}'
+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.
-OK, the last one was actually an Obfuscated Perl Contest entry. :-)
+You can read more about profiling in I<Programming Perl>, chapter 20,
+or I<Mastering Perl>, chapter 5.
-=head2 Why don't Perl one-liners work on my DOS/Mac/VMS system?
+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 .
-The problem is usually that the command interpreters on those systems
-have rather different ideas about quoting than the Unix shells under
-which the one-liners were created. On some systems, you may have to
-change single-quotes to double ones, which you must I<NOT> do on Unix
-or Plan9 systems. You might also have to change a single % to a %%.
+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 .
-For example:
+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 .
- # Unix
- perl -e 'print "Hello world\n"'
+=head2 How do I cross-reference my Perl programs?
+
+The 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
+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
+
+Of course, if you simply follow the guidelines in L<perlstyle>,
+you shouldn't need to reformat. The habit of formatting your code
+as you write it will help prevent bugs. Your editor can and should
+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
+the following settings in vi and its clones:
+
+ set ai sw=4
+ map! ^O {^M}^[O^T
- # DOS, etc.
- perl -e "print \"Hello world\n\""
+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
+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.
+
+=head2 Is there a ctags for Perl?
+
+(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.
+
+Exuberent 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?
- # Mac
- print "Hello world\n"
- (then Run "Myscript" or Shift-Command-R)
+Perl programs are just plain text, so any editor will do.
- # VMS
- perl -e "print ""Hello world\n"""
+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.
-The problem is that none of this is reliable: it depends on the
-command interpreter. Under Unix, the first two often work. Under DOS,
-it's entirely possible neither works. If 4DOS was the command shell,
-you'd probably have better luck like this:
+If you want an IDE, check the following (in alphabetical order, not
+order of preference):
- perl -e "print <Ctrl-x>"Hello world\n<Ctrl-x>""
+=over 4
-Under the Mac, it depends which environment you are using. The MacPerl
-shell, or MPW, is much like Unix shells in its support for several
-quoting variants, except that it makes free use of the Mac's non-ASCII
-characters as control characters.
+=item Eclipse
-Using qq(), q(), and qx(), instead of "double quotes", 'single
-quotes', and `backticks`, may make one-liners easier to write.
+http://e-p-i-c.sf.net/
-There is no general solution to all of this. It is a mess, pure and
-simple. Sucks to be away from Unix, huh? :-)
+The Eclipse Perl Integration Project integrates Perl
+editing/debugging with Eclipse.
-[Some of this answer was contributed by Kenneth Albanowski.]
+=item Enginsite
-=head2 Where can I learn about CGI or Web programming in Perl?
+http://www.enginsite.com/
-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 these sources:
+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.
- WWW Security FAQ
- http://www.w3.org/Security/Faq/
+=item Komodo
- Web FAQ
- http://www.boutell.com/faq/
+http://www.ActiveState.com/Products/Komodo/
- CGI FAQ
- http://www.webthing.com/page.cgi/cgifaq
+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 Spec
- http://www.w3.org/pub/WWW/Protocols/HTTP/
+=item Open Perl IDE
- HTML Spec
- http://www.w3.org/TR/REC-html40/
- http://www.w3.org/pub/WWW/MarkUp/
+http://open-perl-ide.sourceforge.net/
- CGI Spec
- http://www.w3.org/CGI/
+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.
- CGI Security FAQ
- http://www.go2net.com/people/paulp/cgi-security/safe-cgi.txt
+=item OptiPerl
+http://www.optiperl.com/
-=head2 Where can I learn about object-oriented Perl programming?
+OptiPerl is a Windows IDE with simulated CGI environment, including
+debugger and syntax highlighting editor.
-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/ .
+=item Padre
-=head2 Where can I learn about linking C with Perl? [h2xs, xsubpp]
+http://padre.perlide.org/
-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
-call Perl from C, then read L<perlembed>, L<perlcall>, and
-L<perlguts>. Don't forget that you can learn a lot from looking at
-how the authors of existing extension modules wrote their code and
-solved their problems.
+Padre is cross-platform IDE for Perl written in Perl using the the wxWidgets
+to provide a native look and feel. It's open source under the Artistic
+License.
-=head2 I've read perlembed, perlguts, etc., but I can't embed perl in
-my C program, what am I doing wrong?
+=item PerlBuilder
-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 bug report with the output of
-C<make test TEST_VERBOSE=1> along with C<perl -V>.
+http://www.solutionsoft.com/perl.htm
-=head2 When I tried to run my script, I got this message. What does it
-mean?
+PerlBuilder is an integrated development environment for Windows that
+supports Perl development.
-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:
+=item visiPerl+
- perl program 2>diag.out
- splain [-v] [-p] diag.out
+http://helpconsulting.net/visiperl/
-or change your program to explain the messages for you:
+From Help Consulting, for Windows.
- use diagnostics;
+=item Visual Perl
-or
+http://www.activestate.com/Products/Visual_Perl/
- use diagnostics -verbose;
+Visual Perl is a Visual Studio.NET plug-in from ActiveState.
-=head2 What's MakeMaker?
+=item Zeus
-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>.
+http://www.zeusedit.com/lookmain.html
-=head1 AUTHOR AND COPYRIGHT
+Zeus for Window is another Win32 multi-language editor/IDE
+that comes with support for Perl:
-Copyright (c) 1997-1999 Tom Christiansen and Nathan Torkington.
-All rights reserved.
+=back
-When included as an integrated part of the Standard Distribution
-of Perl or of its documentation (printed or otherwise), this works is
-covered under Perl's Artistic License. For separate distributions of
-all or part of this FAQ outside of that, see L<perlfaq>.
+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.
-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
-be courteous but is not required.
+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 te
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