* FAQ sync for Nov blead release

This comes from 028b6d17a07335707c2b234cb69ac4051ed48435 in
git@github.com:briandfoy/perlfaq.git

1 files changed, 747 insertions, 11 deletions

diff --git a/pod/perlfaq3.pod b/pod/perlfaq3.pod
index 8ddcabb370..c1ba5bb1b0 100644
--- a/pod/perlfaq3.pod
+++ b/pod/perlfaq3.pod
@@ -67,14 +67,14 @@ 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 cna use to re-install every module:
+that C<CPAN.pm> understands and can 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).
+as "Perl" (although you can get those with C<Module::CoreList>).
 
 	use ExtUtils::Installed;
 
@@ -82,7 +82,7 @@ as "Perl" (although you can get those with Module::CoreList).
 	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;
 
@@ -94,7 +94,7 @@ can use File::Find::Rule.
 		;
 
 If you do not have that module, you can do the same thing
-with File::Find which is part of the standard library.
+with File::Find which is part of the standard library:
 
 	use File::Find;
 	my @files;
@@ -117,12 +117,12 @@ 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).
+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 finds it:
 
 	$ perl -MModule::Name -e1
 
@@ -307,6 +307,10 @@ 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 Notepad++
+
+http://notepad-plus.sourceforge.net/
+
 =item Open Perl IDE
 
 http://open-perl-ide.sourceforge.net/
@@ -326,9 +330,8 @@ debugger and syntax highlighting editor.
 
 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.
+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
 
@@ -364,7 +367,740 @@ 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
+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
\ No newline at end of file
+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
+
+=item GNU Emacs
+
+http://www.gnu.org/software/emacs/windows/ntemacs.html
+
+=item MicroEMACS
+
+http://www.microemacs.de/
+
+=item XEmacs
+
+http://www.xemacs.org/Download/index.html
+
+=item Jed
+
+http://space.mit.edu/~davis/jed/
+
+=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://dickey.his.com/vile/vile.html
+
+=item Vim
+
+http://www.vim.org/
+
+=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/IDEs that support Perl:
+
+=over 4
+
+=item Codewright
+
+http://www.borland.com/codewright/
+
+=item MultiEdit
+
+http://www.MultiEdit.com/
+
+=item SlickEdit
+
+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://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.
+
+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.mkssoftware.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
+
+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 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
+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 Affrus
+
+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
+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
+
+=head2 Where can I get Perl macros for vi?
+
+For a complete version of Tom Christiansen's vi configuration file,
+see http://www.cpan.org/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.cpan.org/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.cpan.org/authors/Tom_Christiansen/scripts/rep.gz ;
+this program repeats a command and updates the screen as needed, rendering
+B<rep ps axu> similar to B<top>.
+
+=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 plaform: 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.
+
+=item CamelBones
+
+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?
+
+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
+I<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.  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.
+
+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).
+
+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.
+
+The undump program was an ancient attempt to speed up 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>.
+
+Of course, the best way to save memory is to not do anything to waste
+it in the first place. Good programming practices can go a long way
+toward this:
+
+=over 4
+
+=item * Don't slurp!
+
+Don't read an entire file into memory if you can process it line
+by line. Or more concretely, use a loop like this:
+
+	#
+	# Good Idea
+	#
+	while (<FILE>) {
+	   # ...
+	}
+
+instead of this:
+
+	#
+	# Bad Idea
+	#
+	@data = <FILE>;
+	foreach (@data) {
+	    # ...
+	}
+
+When the files you're processing are small, it doesn't much matter which
+way you do it, but it makes a huge difference when they start getting
+larger.
+
+=item * Use map and grep selectively
+
+Remember that both map and grep expect a LIST argument, so doing this:
+
+        @wanted = grep {/pattern/} <FILE>;
+
+will cause the entire file to be slurped. For large files, it's better
+to loop:
+
+        while (<FILE>) {
+                push(@wanted, $_) if /pattern/;
+        }
+
+=item * Avoid unnecessary quotes and stringification
+
+Don't quote large strings unless absolutely necessary:
+
+        my $copy = "$large_string";
+
+makes 2 copies of $large_string (one for $copy and another for the
+quotes), whereas
+
+        my $copy = $large_string;
+
+only makes one copy.
+
+Ditto for stringifying large arrays:
+
+	{
+	local $, = "\n";
+	print @big_array;
+	}
+
+is much more memory-efficient than either
+
+	print join "\n", @big_array;
+
+or
+
+	{
+	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 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.
+
+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
+will incur a penalty in access time, but that's probably better than
+causing your hard disk to thrash due to massive swapping.
+
+=back
+
+=head2 Is it safe to return a reference to local or lexical data?
+
+Yes. Perl's garbage collection system takes care of this so
+everything works out right.
+
+    sub makeone {
+	my @a = ( 1 .. 10 );
+	return \@a;
+    }
+
+    for ( 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?
+
+(contributed by Michael Carman)
+
+You usually can't. Memory allocated to lexicals (i.e. my() variables)
+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() 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-
+exec themselves. Some operating systems (notably, systems that use
+mmap(2) for allocating large chunks of memory) can reclaim memory that
+is no longer used, but on such systems, perl must be configured and
+compiled to use the OS's malloc, not perl's.
+
+In general, memory allocation and de-allocation isn't something you can
+or should be worrying about much in Perl.
+
+See also "How can I make my Perl program take less memory?"
+
+=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.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".
+
+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 (Starting from Perl
+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 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
+the B:: hierarchy.  The B::Deparse module should be able to
+defeat most attempts to hide source.  Again, this is not
+unique to 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?
+
+(contributed by brian d foy)
+
+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
+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
+(but see L<How can I make my Perl program run faster?>).
+
+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.
+
+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 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<ALTERNATE_SHEBANG> (see the
+F<dosish.h> 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>.
+
+Under "Classic" MacOS, a perl program will have the appropriate Creator and
+Type, so that double-clicking them will invoke the MacPerl application.
+Under Mac OS X, clickable apps can be made from any C<#!> script using Wil
+Sanchez' DropScript utility: http://www.wsanchez.net/software/ .
+
+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 (including Mac OS X)
+    perl -e 'print "Hello world\n"'
+
+    # DOS, etc.
+    perl -e "print \"Hello world\n\""
+
+    # Mac Classic
+    print "Hello world\n"
+     (then Run "Myscript" or Shift-Command-R)
+
+    # MPW
+    perl -e 'print "Hello world\n"'
+
+    # 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.
+
+[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 the troubleshooting
+guides and references in L<perlfaq9> or in the CGI MetaFAQ:
+
+	http://www.perl.org/CGI_MetaFAQ.html
+
+=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>, L<perltoot>, L<perltooc>, and L<perlbot> for reference.
+
+A good book on OO on Perl is the "Object-Oriented Perl"
+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?
+
+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.
+
+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
+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?
+
+(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 REVISION
+
+Revision: $Revision$
+
+Date: $Date$
+
+See L<perlfaq> for source control details and availability.
+
+=head1 AUTHOR AND COPYRIGHT
+
+Copyright (c) 1997-2009 Tom Christiansen, Nathan Torkington, and
+other authors as noted. All rights reserved.
+
+This documentation is free; you can redistribute it and/or modify it
+under the same terms as Perl itself.
+
+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.