Obtaining Online Information

Perl is one the most heavily documented languages in the known Universe! This appendix only scratches the surface. Fortunately, there exists a wealth of online information that comes automatically with Perl. To get going, type the following command:

$ perldoc perl

This will provide you with a complete list of the many available Perl manpages. The most important of these, besides perldoc perl itself, are listed in Table A-1.

Table A-1. The main Perl manpage documents

Manpage	Description
perltoc	Table of contents for the manpages
perlsyn	Perl syntax
perldata	Data structures
perlop	Operators and precedence
perlrequick, perlretut, perlre	Regular expressions; see Appendix C
perlvar	Predefined variables
perlsub	Subroutines
perlfunc	Built-in functions
perlreftut, perlref	Perl references
perlmod, perlobj	Modules and objects
perlipc	Inter-process communication
perlrun	Perl execution and options
perldebug, perldiag	Debugging and diagnostics
perlsec	Perl security
perlstyle	The Perl style guide
perltrap	Traps for the unwary

There used to be only a single perlfaq page, listing all the Frequently Asked Questions for Perl, but although this page still exists, its original information has been greatly expanded into the nine FAQs detailed in Table A-2. Again, access these with the perldoc perlfaq syntax.

Table A-2. The Perl FAQ documents

Manpage	Description
perlfaq	An FAQ overview
perlfaq1	General questions about Perl
perlfaq2	Obtaining and learning about Perl
perlfaq3	Programming tools
perlfaq4	Data manipulation
perlfaq5	Files and formats
perlfaq6	Regular expressions; see Appendix C
perlfaq7	Perl language issues
perlfaq8	System interaction
perlfaq9	Networking

There are also various notes for different operating systems. The main platforms covered are listed in Table A-3.

Table A-3. Operating system documentation

Manpage	Description
perlaix	Notes for AIX
perlsolaris	Notes for Solaris
perlhpux	Notes for HP-UX
perlcygwin	Notes for Cygwin
perlvms	Notes for VMS
perldos	Notes for DOS
perlwin32	Notes for Windows
perlos2	Notes for OS/2
perlos390	Notes for OS/390

Virtually every CPAN module author also provides his or her own self-installing perldoc notes for the manpage library. As an example, let's look at the first few rows of the documentation provided for DBD::Oracle:

$ perldoc DBD::Oracle
  
NAME
    DBD::Oracle - Oracle database driver for the DBI module
  
SYNOPSIS
      use DBI;
  
      $dbh = DBI->connect("dbi:Oracle:$dbname", $user, $passwd);
...

Finally, if there's a particular built-in function you're interested in, you can run perldoc with the -f function switch, to interrogate it:

$ perldoc -f printf
  
printf FILEHANDLE FORMAT, LIST
printf FORMAT, LIST
   Equivalent to "print FILEHANDLE sprintf(FORMAT, LIST)", except
   that "$\" (the output record separator) is not appended. The
   first argument of the list will be interpreted as the "printf"
   format. If "use locale" is in effect, the character used for the
   decimal point in formatted real numbers is affected by the
   LC_NUMERIC locale. See the perllocale manpage.
  
   Don't fall into the trap of using a "printf" when a simple
   "print" would do. The "print" is more efficient and less error
   prone.

For more online information, try http://www.perl.com or http://www.cpan.org.

Of course, there are also many excellent printed books describing the Perl language for both beginners and advanced developers. See Chapter 1 for some suggestions.