=head1 NAME perlfaq3 - Programming Tools =head1 DESCRIPTION This section of the FAQ answers questions related to programmer tools and programming support. =head2 How do I do (anything)? Have you looked at CPAN (see L)? The chances are that someone has already written a module that can solve your problem. Have you read the appropriate manpages? Here's a brief index: Basics perldata, perlvar, perlsyn, perlop, perlsub Execution perlrun, perldebug Functions perlfunc Objects perlref, perlmod, perlobj, perltie Data Structures perlref, perllol, perldsc Modules perlmod, perlmodlib, perlsub Regexes perlre, perlfunc, perlop, perllocale Moving to perl5 perltrap, perl Linking w/C perlxstut, perlxs, perlcall, perlguts, perlembed 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 manpage set is found in L. =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: perl -de 42 Now just type in any legal Perl code, and it will be immediately evaluated. You can also examine the symbol table, get stack backtraces, check variable values, set breakpoints, and other operations typically found in symbolic debuggers. =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://sourceforge.net/projects/psh/ . 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. 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. =head2 How do I find which modules are installed on my system? From the command line, you can use the C command's C<-l> switch: $ cpan -l You can also use C's C<-a> switch to create an autobundle file that C understands and cna use to re-install every module: $ cpan -a 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). use ExtUtils::Installed; my $inst = ExtUtils::Installed->new(); my @modules = $inst->modules(); If you want a list of all of the Perl module filenames, you can use File::Find::Rule. use File::Find::Rule; 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( { 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 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). $ perldoc Module::Name You can also try to include the module in a one-liner to see if perl finds it. $ perl -MModule::Name -e1 =head2 How do I debug my Perl programs? (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 and L. #!/usr/bin/perl use strict; use warnings; Beyond that, the simplest debugger is the C function. Use it to look at values as you run your program: print STDERR "The value is [$value]\n"; The C module can pretty-print Perl data structures: 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. If you'd like a graphical user interface and you have Tk, you can use C. 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 namespace has several modules which you can use to profile your Perl programs. The C 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, you'll get a F file with the profile data. To look at the data, you can turn it into a human-readable report with the C program that comes with C. dprofpp You can also do the profiling and reporting in one step with the C<-p> switch to : dprofpp -p program.pl The C (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: perl -d:NYTProf some_perl.pl Like C, it creates a database of the profile information that you can turn into reports. The C command turns the data into an HTML report similar to the C report: nytprofhtml CPAN has several other profilers that you can invoke in the same fashion. You might also be interested in using the C to measure and compare code snippets. You can read more about profiling in I, chapter 20, or I, chapter 5. L documents creating a custom debugger if you need to create a special sort of profiler. brian d foy describes the process in I, "Creating a Perl Debugger", http://www.ddj.com/184404522 , and "Profiling in Perl" http://www.ddj.com/184404580 . 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, http://www.stonehenge.com/merlyn/UnixReview/col49.html , and "Profiling in Template Toolkit via Overriding" for I, 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 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. 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, 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 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? 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 philosophy is the philosophy of several small tools that each do one thing and do it well. It's like a carpenter's toolbox. If you want an IDE, check the following (in alphabetical order, not order of preference): =over 4 =item Eclipse http://e-p-i-c.sf.net/ The Eclipse Perl Integration Project integrates Perl editing/debugging with Eclipse. =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. =item Open Perl IDE 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/ 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 the the wxWidgets to provide a native look and feel. It's open source under the Artistic License. =item PerlBuilder http://www.solutionsoft.com/perl.htm PerlBuilder is an integrated development environment for Windows that supports Perl development. =item visiPerl+ http://helpconsulting.net/visiperl/ From Help Consulting, for Windows. =item 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 te