实用报表提取语言 Perl : Practical Extraction and Report Language

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Perl 最初的设计者为 拉里·沃尔（Larry Wall），他于1987年12月18日发表。Perl借取了C、sed、awk、shell scripting以及很多其他程序语言的特性。其中最重要的特性是它内部集成了 正则表达式的功能，以及巨大的第三方代码库CPAN。简而言之，Perl象C一样强大，象awk、sed等 脚本描述语言一样方便。Perl 一般被称为“实用报表提取语言”（Practical Extraction and Report Language），你也可能看到“perl”，所有的字母都是小写的。一般，“Perl”，有大写的 P，是指语言本身，而“perl”，小写的 p，是指程序运行的 解释器。

perl的前身是Unix系统管理的一个工具，被用在无数的小任务里。后逐渐发展成为一种功能强大的程序设计语言，用作Web编程、数据库处理、XML处理以及系统管理；在完成这些工作时，同时仍能处理日常细小工作，这是它的设计初衷。Perl特别适合系统管理和Web编程。实际上已经被用在所有Unix(包括Linux)捆绑在一起作为标准部件发布，同时也用在Microsoft Windows和几乎其他所有操作系统。Perl的应用很广泛，依靠Perl工作更容易、更有效。

　　NAME
     perl - Practical Extraction and Report Language
　　SYNOPSIS
     perl [ -sTtuUWX ] [ -hv ] [ -V[:*configvar*] ]
     [ -cw ] [ -d[t][:*debugger*] ] [ -D[*number/list*] ]
     [ -pna ] [ -F*pattern* ] [ -l[*octal*] ] [ -0[*octal/hexadecimal*] ]
     [ -I*dir* ] [ -m[-]*module* ] [ -M[-]*'module...'* ] [ -f ]
     [ -C [*number/list*] ] [ -P ] [ -S ] [ -x[*dir*] ] [ -i[*extension*] ]
     [ -e *'command'* ] [ -- ] [ *programfile* ] [ *argument* ]...
　　If you're new to Perl, you should start with perlintro, which is a
     general intro for beginners and provides some background to help you
     navigate the rest of Perl's extensive documentation.
　　For ease of access, the Perl manual has been split up into several
     sections.
　　Overview
         perl                Perl overview (this section)
         perlintro           Perl introduction for beginners
         perltoc             Perl documentation table of contents
　　ActivePerl          ActivePerl overview
　　Tutorials
         perlreftut          Perl references short introduction
         perldsc             Perl data structures intro
         perllol             Perl data structures: arrays of arrays
　　perlrequick         Perl regular expressions quick start
         perlretut           Perl regular expressions tutorial
　　perlboot            Perl OO tutorial for beginners
         perltoot            Perl OO tutorial, part 1
         perltooc            Perl OO tutorial, part 2
         perlbot             Perl OO tricks and examples
　　perlstyle           Perl style guide
　　perlcheat           Perl cheat sheet
         perltrap            Perl traps for the unwary
         perldebtut          Perl debugging tutorial
　　perlfaq             Perl frequently asked questions
           perlfaq1          General Questions About Perl
           perlfaq2          Obtaining and Learning about Perl
           perlfaq3          Programming Tools
           perlfaq4          Data Manipulation
           perlfaq5          Files and Formats
           perlfaq6          Regexes
           perlfaq7          Perl Language Issues
           perlfaq8          System Interaction
           perlfaq9          Networking
　　Reference Manual
         perlsyn             Perl syntax
         perldata            Perl data structures
         perlop              Perl operators and precedence
         perlsub             Perl subroutines
         perlfunc            Perl built-in functions
           perlopentut       Perl open() tutorial
           perlpacktut       Perl pack() and unpack() tutorial
         perlpod             Perl plain old documentation
         perlpodspec         Perl plain old documentation format specification
         perlrun             Perl execution and options
         perldiag            Perl diagnostic messages
         perllexwarn         Perl warnings and their control
         perldebug           Perl debugging
         perlvar             Perl predefined variables
         perlre              Perl regular expressions, the rest of the story
         perlreref           Perl regular expressions quick reference
         perlref             Perl references, the rest of the story
         perlform            Perl formats
         perlobj             Perl objects
         perltie             Perl objects hidden behind simple variables
           perldbmfilter     Perl DBM filters
　　perlipc             Perl interprocess communication
         perlfork            Perl fork() information
         perlnumber          Perl number semantics
　　perlthrtut          Perl threads tutorial
           perlothrtut       Old Perl threads tutorial
　　perlport            Perl portability guide
         perllocale          Perl locale support
         perluniintro        Perl Unicode introduction
         perlunicode         Perl Unicode support
         perlebcdic          Considerations for running Perl on EBCDIC platforms
　　perlsec             Perl security
　　perlmod             Perl modules: how they work
         perlmodlib          Perl modules: how to write and use
         perlmodstyle        Perl modules: how to write modules with style
         perlmodinstall      Perl modules: how to install from CPAN
         perlnewmod          Perl modules: preparing a new module for distribution
　　perlutil            utilities packaged with the Perl distribution
　　perlcompile         Perl compiler suite intro
　　perlfilter          Perl source filters
　　perlglossary        Perl Glossary
　　Internals and C Language Interface
         perlembed           Perl ways to embed perl in your C or C++ application
         perldebguts         Perl debugging guts and tips
         perlxstut           Perl XS tutorial
         perlxs              Perl XS application programming interface
         perlclib            Internal replacements for standard C library functions
         perlguts            Perl internal functions for those doing extensions
         perlcall            Perl calling conventions from C
　　perlapi             Perl API listing (autogenerated)
         perlintern          Perl internal functions (autogenerated)
         perliol             C API for Perl's implementation of IO in Layers
         perlapio            Perl internal IO abstraction interface
　　perlhack            Perl hackers guide
　　Miscellaneous
         perlbook            Perl book information
         perltodo            Perl things to do
　　perldoc             Look up Perl documentation in Pod format
　　perlhist            Perl history records
         perldelta           Perl changes since previous version
         perl587delta        Perl changes in version 5.8.7
         perl586delta        Perl changes in version 5.8.6
         perl585delta        Perl changes in version 5.8.5
         perl584delta        Perl changes in version 5.8.4
         perl583delta        Perl changes in version 5.8.3
         perl582delta        Perl changes in version 5.8.2
         perl581delta        Perl changes in version 5.8.1
         perl58delta         Perl changes in version 5.8.0
         perl573delta        Perl changes in version 5.7.3
         perl572delta        Perl changes in version 5.7.2
         perl571delta        Perl changes in version 5.7.1
         perl570delta        Perl changes in version 5.7.0
         perl561delta        Perl changes in version 5.6.1
         perl56delta         Perl changes in version 5.6
         perl5005delta       Perl changes in version 5.005
         perl5004delta       Perl changes in version 5.004
　　activeperl-release  Release notes for ActivePerl
         activeperl-changes  ActivePerl revision history
　　perlartistic        Perl Artistic License
         perlgpl             GNU General Public License
　　Language-Specific
         perlcn              Perl for Simplified Chinese (in EUC-CN)
         perljp              Perl for Japanese (in EUC-JP)
         perlko              Perl for Korean (in EUC-KR)
         perltw              Perl for Traditional Chinese (in Big5)
　　Platform-Specific
         perlaix             Perl notes for AIX
         perlamiga           Perl notes for AmigaOS
         perlapollo          Perl notes for Apollo DomainOS
         perlbeos            Perl notes for BeOS
         perlbs2000          Perl notes for POSIX-BC BS2000
         perlce              Perl notes for WinCE
         perlcygwin          Perl notes for Cygwin
         perldgux            Perl notes for DG/UX
         perldos             Perl notes for DOS
         perlepoc            Perl notes for EPOC
         perlfreebsd         Perl notes for FreeBSD
         perlhpux            Perl notes for HP-UX
         perlhurd            Perl notes for Hurd
         perlirix            Perl notes for Irix
         perllinux           Perl notes for Linux
         perlmachten         Perl notes for Power MachTen
         perlmacos           Perl notes for Mac OS (Classic)
         perlmacosx          Perl notes for Mac OS X
         perlmint            Perl notes for MiNT
         perlmpeix           Perl notes for MPE/iX
         perlnetware         Perl notes for NetWare
         perlopenbsd         Perl notes for OpenBSD
         perlos2             Perl notes for OS/2
         perlos390           Perl notes for OS/390
         perlos400           Perl notes for OS/400
         perlplan9           Perl notes for Plan 9
         perlqnx             Perl notes for QNX
         perlsolaris         Perl notes for Solaris
         perltru64           Perl notes for Tru64
         perluts             Perl notes for UTS
         perlvmesa           Perl notes for VM/ESA
         perlvms             Perl notes for VMS
         perlvos             Perl notes for Stratus VOS
         perlwin32           Perl notes for Windows
　　By default, the manpages listed above are installed in the
     /usr/local/man/ directory.
　　Extensive additional documentation for Perl modules is available. The
     default configuration for perl will place this additional documentation
     in the /usr/local/lib/perl5/man directory (or else in the man
     subdirectory of the Perl library directory). Some of this additional
     documentation is distributed standard with Perl, but you'll also find
     documentation for third-party modules there.
　　You should be able to view Perl's documentation with your man(1) program
     by including the proper directories in the appropriate start-up files,
     or in the MANPATH environment variable. To find out where the
     configuration has installed the manpages, type:
　　perl -V:man.dir
　　If the directories have a common stem, such as /usr/local/man/man1 and
     /usr/local/man/man3, you need only to add that stem (/usr/local/man) to
     your man(1) configuration files or your MANPATH environment variable. If
     they do not share a stem, you'll have to add both stems.
　　If that doesn't work for some reason, you can still use the supplied
     perldoc script to view module information. You might also look into
     getting a replacement man program.
　　If something strange has gone wrong with your program and you're not
     sure where you should look for help, try the -w switch first. It will
     often point out exactly where the trouble is.
　　DESCRIPTION
     Perl is a language optimized for scanning arbitrary text files,
     extracting information from those text files, and printing reports based
     on that information. It's also a good language for many system
     management tasks. The language is intended to be practical (easy to use,
     efficient, complete) rather than beautiful (tiny, elegant, minimal).
　　Perl combines (in the author's opinion, anyway) some of the best
     features of C, sed, awk, and sh, so people familiar with those languages
     should have little difficulty with it. (Language historians will also
     note some vestiges of csh, Pascal, and even BASIC-PLUS.) Expression
     syntax corresponds closely to C expression syntax. Unlike most Unix
     utilities, Perl does not arbitrarily limit the size of your data--if
     you've got the memory, Perl can slurp in your whole file as a single
     string. Recursion is of unlimited depth. And the tables used by hashes
     (sometimes called "associative arrays") grow as necessary to prevent
     degraded performance. Perl can use sophisticated pattern matching
     techniques to scan large amounts of data quickly. Although optimized for
     scanning text, Perl can also deal with binary data, and can make dbm
     files look like hashes. Setuid Perl scripts are safer than C programs
     through a dataflow tracing mechanism that prevents many stupid security
     holes.
　　If you have a problem that would ordinarily use sed or awk or sh, but it
     exceeds their capabilities or must run a little faster, and you don't
     want to write the silly thing in C, then Perl may be for you. There are
     also translators to turn your sed and awk scripts into Perl scripts.
　　But wait, there's more...
　　Begun in 1993 (see perlhist), Perl version 5 is nearly a complete
     rewrite that provides the following additional benefits:
　　*   modularity and reusability using innumerable modules
　　Described in perlmod, perlmodlib, and perlmodinstall.
　　*   embeddable and extensible
　　Described in perlembed, perlxstut, perlxs, perlcall, perlguts, and
         xsubpp.
　　*   roll-your-own magic variables (including multiple simultaneous DBM
         implementations)
　　Described in perltie and AnyDBM_File.
　　*   subroutines can now be overridden, autoloaded, and prototyped
　　Described in perlsub.
　　*   arbitrarily nested data structures and anonymous functions
　　Described in perlreftut, perlref, perldsc, and perllol.
　　*   object-oriented programming
　　Described in perlobj, perlboot, perltoot, perltooc, and perlbot.
　　*   support for light-weight processes (threads)
　　Described in perlthrtut and threads.
　　*   support for Unicode, internationalization, and localization
　　Described in perluniintro, perllocale and Locale::Maketext.
　　*   lexical scoping
　　Described in perlsub.
　　*   regular expression enhancements
　　Described in perlre, with additional examples in perlop.
　　*   enhanced debugger and interactive Perl environment, with integrated
         editor support
　　Described in perldebtut, perldebug and perldebguts.
　　*   POSIX 1003.1 compliant library
　　Described in POSIX.
　　Okay, that's *definitely* enough hype.
　　AVAILABILITY
     Perl is available for most operating systems, including virtually all
     Unix-like platforms. See "Supported Platforms" in perlport for a
     listing.
　　ENVIRONMENT
     See perlrun.
　　AUTHOR
     Larry Wall <larry@wall.org>, with the help of oodles of other folks.
　　If your Perl success stories and testimonials may be of help to others
     who wish to advocate the use of Perl in their applications, or if you
     wish to simply express your gratitude to Larry and the Perl developers,
     please write to perl-thanks@perl.org .
　　FILES
      "@INC"                 locations of perl libraries
　　SEE ALSO
      a2p    awk to perl translator
      s2p    sed to perl translator
　　http://www.perl.org/       the Perl homepage
      http://www.perl.com/       Perl articles (O'Reilly)
      http://www.cpan.org/       the Comprehensive Perl Archive
      http://www.pm.org/         the Perl Mongers
　　DIAGNOSTICS
     The "use warnings" pragma (and the -w switch) produces some lovely
     diagnostics.
　　See perldiag for explanations of all Perl's diagnostics. The "use
     diagnostics" pragma automatically turns Perl's normally terse warnings
     and errors into these longer forms.
　　Compilation errors will tell you the line number of the error, with an
     indication of the next token or token type that was to be examined. (In
     a script passed to Perl via -e switches, each -e is counted as one
     line.)
　　Setuid scripts have additional constraints that can produce error
     messages such as "Insecure dependency". See perlsec.
　　Did we mention that you should definitely consider using the -w switch?
　　BUGS
     The -w switch is not mandatory.
　　Perl is at the mercy of your machine's definitions of various operations
     such as type casting, atof(), and floating-point output with sprintf().
　　If your stdio requires a seek or eof between reads and writes on a
     particular stream, so does Perl. (This doesn't apply to sysread() and
     syswrite().)
　　While none of the built-in data types have any arbitrary size limits
     (apart from memory size), there are still a few arbitrary limits: a
     given variable name may not be longer than 251 characters. Line numbers
     displayed by diagnostics are internally stored as short integers, so
     they are limited to a maximum of 65535 (higher numbers usually being
     affected by wraparound).
　　You may mail your bug reports (be sure to include full configuration
     information as output by the myconfig program in the perl source tree,
     or by "perl -V") to perlbug@perl.org . If you've succeeded in compiling
     perl, the perlbug script in the utils/ subdirectory can be used to help
     mail in a bug report.
　　Perl actually stands for Pathologically Eclectic Rubbish Lister, but
     don't tell anyone I said that.
　　NOTES
     The Perl motto is "There's more than one way to do it." Divining how
     many more is left as an exercise to the reader.
　　The three principal virtues of a programmer are Laziness, Impatience,
     and Hubris. See the Camel Book for why.