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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.perl.com/CPAN/doc/FMTEYEWTK/index.html - (not a man-page but still useful) - -A crude table of contents for the Perl man page 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: - - 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? - -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. - -=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. - -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>. - -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. - - open(FH, "> /etc/cantwrite") - or die "Couldn't write to /etc/cantwrite: $!\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>. - -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. - -=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. - -Here's a sample use of Benchmark: - - use Benchmark; - - @junk = `cat /etc/motd`; - $count = 10_000; - - timethese($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 }, - }); - -This is what it prints (on one machine--your results will be dependent -on your hardware, operating system, and the load on your machine): - - 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) - -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. - -=head2 How do I cross-reference my Perl programs? - -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. - - perl -MO=Xref[,OPTIONS] scriptname.plx - -=head2 Is there a pretty-printer (formatter) for Perl? - -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. - -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 swears -by the following settings in vi and its clones: - - set ai sw=4 - map! ^O {^M}^[O^T - -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 - -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. - -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? - -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. - -=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 a Windows IDE, check the following: - -=over 4 - -=item CodeMagicCD - -http://www.codemagiccd.com/ - -=item Komodo - -ActiveState's cross-platform, multi-language IDE has Perl support, -including a regular expression debugger and remote debugging -(http://www.ActiveState.com/Products/Komodo/index.html). -(Visual Perl, a Visual Studio.NET plug-in is currently (early 2001) -in beta (http://www.ActiveState.com/Products/VisualPerl/index.html)). - -=item The Object System - -(http://www.castlelink.co.uk/object_system/) is a Perl web -applications development IDE. - -=item PerlBuilder - -(http://www.solutionsoft.com/perl.htm) is an integrated development -environment for Windows that supports Perl development. - -=item Perl code magic - -(http://www.petes-place.com/codemagic.html). - -=item visiPerl+ - -http://helpconsulting.net/visiperl/, from Help Consulting. - -=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. - -For Windows editors: you can download an Emacs - -=over 4 - -=item GNU Emacs - -http://www.gnu.org/software/emacs/windows/ntemacs.html - -=item MicroEMACS - -http://members.nbci.com/uemacs/ - -=item XEmacs - -http://www.xemacs.org/Download/index.html - -=back - -or a vi clone such as - -=over 4 - -=item Elvis - -ftp://ftp.cs.pdx.edu/pub/elvis/ http://www.fh-wedel.de/elvis/ - -=item Vile - -http://vile.cx/ - -=item Vim - -http://www.vim.org/ - -win32: http://www.cs.vu.nl/%7Etmgil/vi.html - -=back - -For vi lovers in general, Windows or elsewhere: -http://www.thomer.com/thomer/vi/vi.html. - -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 -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: - -=over 4 - -=item Codewright - -http://www.starbase.com/ - -=item MultiEdit - -http://www.MultiEdit.com/ - -=item SlickEdit - -http://www.slickedit.com/ - -=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 -acts as a development environment of sorts. Perl Composer -(http://perlcomposer.sourceforge.net/vperl.html) is an IDE for Perl/Tk -GUI creation. - -In addition to an editor/IDE you might be interested in a more -powerful shell environment for Win32. Your options include - -=over 4 - -=item Bash - -from the Cygwin package (http://sources.redhat.com/cygwin/) - -=item Ksh - -from the MKS Toolkit (http://www.mks.com/), or the Bourne shell of -the U/WIN environment (http://www.research.att.com/sw/tools/uwin/) - -=item Tcsh - -ftp://ftp.astron.com/pub/tcsh/, see also -http://www.primate.wisc.edu/software/csh-tcsh-book/ - -=item Zsh - -ftp://ftp.blarg.net/users/amol/zsh/, see also 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. - -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 -appropriately converted. - -On Mac OS the MacPerl Application comes with a simple 32k text editor -that behaves like a rudimentary IDE. In contrast to the MacPerl Application -the MPW Perl tool can make use of the MPW Shell itself as an editor (with -no 32k limit). - -=over 4 - -=item BBEdit and BBEdit Lite - -are text editors for Mac OS that have a Perl sensitivity mode -(http://web.barebones.com/). - -=item Alpha - -is an editor, written and extensible in Tcl, that nonetheless has -built in support for several popular markup and programming languages -including Perl and HTML (http://alpha.olm.net/). - -=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, -see http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/toms.exrc.gz , -the standard benchmark file for vi emulators. The file 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 question on ``How can I make my Perl program run faster?'' - -=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. 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, -modules that have critical sections can be 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--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 that space 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/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. - -=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 (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 (even running 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 can make your -situation worse. 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 also integrate Java and Perl with the -Perl Resource Kit from O'Reilly and Associates. 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. - -=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 cygwin 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. - -=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.) - - # sum first and last fields - perl -lane 'print $F[0] + $F[-1]' * - - # identify text files - perl -le 'for(@ARGV) {print if -f && -T _}' * - - # remove (most) comments from C program - perl -0777 -pe 's{/\*.*?\*/}{}gs' foo.c - - # make file a month younger than today, defeating reaper daemons - perl -e '$X=24*60*60; utime(time(),time() + 30 * $X,@ARGV)' * - - # find first unused uid - perl -le '$i++ while getpwuid($i); print $i' - - # display reasonable manpath - echo $PATH | perl -nl -072 -e ' - s![^/+]*$!man!&&-d&&!$s{$_}++&&push@m,$_;END{print"@m"}' - -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? - -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 %%. - -For example: - - # Unix - perl -e 'print "Hello world\n"' - - # DOS, etc. - perl -e "print \"Hello world\n\"" - - # Mac - print "Hello world\n" - (then Run "Myscript" or Shift-Command-R) - - # VMS - perl -e "print ""Hello world\n""" - -The problem is that none of these examples are reliable: they depend on the -command interpreter. Under Unix, the first two often work. Under DOS, -it's entirely possible that neither works. If 4DOS was the command shell, -you'd probably have better luck like this: - - perl -e "print <Ctrl-x>"Hello world\n<Ctrl-x>"" - -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. - -Using qq(), q(), and qx(), instead of "double quotes", 'single -quotes', and `backticks`, may make one-liners easier to write. - -There is no general solution to all of this. It is a mess, pure and -simple. Sucks to be away from Unix, huh? :-) - -[Some of this answer was contributed by Kenneth Albanowski.] - -=head2 Where can I learn about CGI or Web programming in Perl? - -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: - - WWW Security FAQ - http://www.w3.org/Security/Faq/ - - Web FAQ - http://www.boutell.com/faq/ - - CGI FAQ - http://www.webthing.com/tutorials/cgifaq.html - - HTTP Spec - http://www.w3.org/pub/WWW/Protocols/HTTP/ - - HTML Spec - http://www.w3.org/TR/REC-html40/ - http://www.w3.org/pub/WWW/MarkUp/ - - CGI Spec - http://www.w3.org/CGI/ - - CGI Security FAQ - http://www.go2net.com/people/paulp/cgi-security/safe-cgi.txt - -=head2 Where can I learn about object-oriented Perl programming? - -A good place to start is L<perltoot>, and you can use L<perlobj>, -L<perlboot>, and L<perlbot> for reference. Perltoot didn't come out -until the 5.004 release; you can get a copy (in pod, html, or -postscript) from http://www.perl.com/CPAN/doc/FMTEYEWTK/ . - -=head2 Where can I learn about linking C with Perl? [h2xs, xsubpp] - -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. - -=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 -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>. - -=head2 When I tried to run my script, I got this message. What does it -mean? - -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 - -or change your program to explain the messages for you: - - use diagnostics; - -or - - use diagnostics -verbose; - -=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>. - -=head1 AUTHOR AND COPYRIGHT - -Copyright (c) 1997-1999 Tom Christiansen and Nathan Torkington. -All rights reserved. - -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>. - -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. |
