perl-5.005(1p)

perl-5.0051p

Practical extraction and report language

Usage

perl [-sTuU] [-hv] [-V [:configvar]] [-cw] [-d [:debugger]] [-D [number/list]] [-pna] [-Fpattern] [-l [octal]] [-0 [octal]] [-Idir] [-m [-] module] [-M [-] 'module ... '] [-P] [-S] [-x [dir]] [-i [extension]] [-e 'command'] [--] [programfile] [argument] ...

perl Perl overview (this section)

perldelta Perl changes since previous version

perl5004delta Perl changes in version 5.004

perlfaq Perl frequently asked questions

perltoc Perl documentation table of contents

perldata Perl data structures

perlsyn Perl syntax

perlop Perl operators and precedence

perlre Perl regular expressions

perlrun Perl execution and options

perlfunc Perl builtin functions

perlopentut Perl open() tutorial

perlvar Perl predefined variables

perlsub Perl subroutines

perlmod Perl modules: how they work

perlmodlib Perl modules: how to write and use

perlmodinstall Perl modules: how to install from CPAN

perlform Perl formats

perllocale Perl locale support

perlref Perl references

perlreftut Perl references short introduction

perldsc Perl data structures intro

perllol Perl data structures: lists of lists

perltoot Perl OO tutorial

perlobj Perl objects

perltie Perl objects hidden behind simple variables

perlbot Perl OO tricks and examples

perlipc Perl interprocess communication

perlthrtut Perl threads tutorial

perldebug Perl debugging

perldiag Perl diagnostic messages

perlsec Perl security

perltrap Perl traps for the unwary

perlport Perl portability guide

perlstyle Perl style guide

perlpod Perl plain old documentation

perlbook Perl book information

perlembed Perl ways to embed perl in your C or C++ application

perlapio Perl internal IO abstraction interface

perlxs Perl XS application programming interface

perlxstut Perl XS tutorial

perlguts Perl internal functions for those doing extensions

perlcall Perl calling conventions from C

perlhist Perl history records

perl -V:man.dir

Overview

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 quite 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 very 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 which 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...

Perl version 5 is nearly a complete rewrite, and provides the following additional benefits:

• Many usability enhancements

It is now possible to write much more readable Perl code (even within regular expressions). Formerly cryptic variable names can be replaced by mnemonic identifiers. Error messages are more informative, and the optional warnings will catch many of the mistakes a novice might make. This cannot be stressed enough. Whenever you get mysterious behavior, try the -w switch!!! Whenever you don't get mysterious behavior, try using -w anyway.

• Simplified grammar

The new yacc grammar is one half the size of the old one. Many of the arbitrary grammar rules have been regularized. The number of reserved words has been cut by 2/3. Despite this, nearly all old Perl scripts will continue to work unchanged.

• Lexical scoping

Perl variables may now be declared within a lexical scope, like "auto" variables in C. Not only is this more efficient, but it contributes to better privacy for "programming in the large". Anonymous subroutines exhibit deep binding of lexical variables (closures).

• Arbitrarily nested data structures

Any scalar value, including any array element, may now contain a reference to any other variable or subroutine. You can easily create anonymous variables and subroutines. Perl manages your reference counts for you.

• Modularity and reusability

The Perl library is now defined in terms of modules which can be easily shared among various packages. A package may choose to import all or a portion of a module's published interface. Pragmas (that is, compiler directives) are defined and used by the same mechanism.

• Object-oriented programming

A package can function as a class. Dynamic multiple inheritance and virtual methods are supported in a straightforward manner and with very little new syntax. Filehandles may now be treated as objects.

• Embeddable and Extensible

Perl may now be embedded easily in your C or C++ application, and can either call or be called by your routines through a documented interface. The XS preprocessor is provided to make it easy to glue your C or C++ routines into Perl. Dynamic loading of modules is supported, and Perl itself can be made into a dynamic library.

• POSIX compliant

A major new module is the POSIX module, which provides access to all available POSIX routines and definitions, via object classes where appropriate.

• Package constructors and destructors

The new BEGIN and END blocks provide means to capture control as a package is being compiled, and after the program exits. As a degenerate case they work just like awk's BEGIN and END when you use the -p or -n switches.

• Multiple simultaneous DBM implementations

A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB files from the same script simultaneously. In fact, the old dbmopen interface has been generalized to allow any variable to be tied to an object class which defines its access methods.

• Subroutine definitions may now be autoloaded

In fact, the AUTOLOAD mechanism also allows you to define any arbitrary semantics for undefined subroutine calls. It's not for just autoloading.

• Regular expression enhancements

You can now specify nongreedy quantifiers. You can now do grouping without creating a backreference. You can now write regular expressions with embedded whitespace and comments for readability. A consistent extensibility mechanism has been added that is upwardly compatible with all old regular expressions.

• Innumerable Unbundled Modules

The Comprehensive Perl Archive Network described in the perlmodlib manpage contains hundreds of plug-and-play modules full of reusable code. See http://www.perl.com/CPAN for a site near you.

• Compilability

While not yet in full production mode, a working perl-to-C compiler does exist. It can generate portable byte code, simple C, or optimized C code.

Okay, that's definitely enough hype.

Environment

See the perlrun manpage.

Files

 "@INC"                 locations of perl libraries

Diagnostics

The -w switch produces some lovely diagnostics.

See the perldiag manpage 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 the case of 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 the perlsec manpage.

Did we mention that you should definitely consider using the -w switch?

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.

Availability

Perl is available for the vast majority of operating system platforms, including most Unix-like platforms. The following situation is as of February 1999 and Perl 5.005_03.

The following platforms are able to build Perl from the standard source code distribution available at http://www.perl.com/CPAN/src/index.html

        AIX             Linux           SCO ODT/OSR
        A/UX            MachTen         Solaris
        BeOS            MPE/iX          SunOS
        BSD/OS          NetBSD          SVR4
        DG/UX           NextSTEP        Tru64 UNIX      3)
        DomainOS        OpenBSD         Ultrix
        DOS DJGPP 1)    OpenSTEP        UNICOS
        DYNIX/ptx       OS/2            VMS
        FreeBSD         OS390     2)    VOS
        HP-UX           PowerMAX        Windows 3.1     1)
        Hurd            QNX             Windows 95      1) 4)
        IRIX                            Windows 98      1) 4)
                                        Windows NT      1) 4)
        1) in DOS mode either the DOS or OS/2 ports can be used
        2) formerly known as MVS
        3) formerly known as Digital UNIX and before that DEC OSF/1
        4) compilers: Borland, Cygwin32, Mingw32 EGCS/GCC, VC++

The following platforms have been known to build Perl from the source but for the Perl release 5.005_03 we haven't been able to verify them, either because the hardware/software platforms are rather rare or because we don't have an active champion on these platforms, or both.

3b1 FPS Plan 9
AmigaOS GENIX PowerUX
ConvexOS Greenhills RISC/os
CX/UX ISC Stellar
DC/OSx MachTen 68k SVR2
DDE SMES MiNT TI1500
DOS EMX MPC TitanOS
Dynix NEWS-OS UNICOS/mk
EP/IX Opus Unisys Dynix
ESIX Unixware

The following platforms are planned to be supported in the standard source code distribution of the Perl release 5.006 but are not supported in the Perl release 5.005_03:

        BS2000
        Netware
        Rhapsody
        VM/ESA

The following platforms have their own source code distributions and binaries available via http://www.perl.com/CPAN/ports/index.html.

                                Perl release
        AS/400                  5.003
        MacOS                   5.004
        Netware                 5.003_07
        Tandem Guardian         5.004

The following platforms have only binaries available via http://www.perl.com/CPAN/ports/index.html.

                                Perl release
        Acorn RISCOS            5.005_02
        AOS                     5.002
        LynxOS                  5.004_02

Author

Larry Wall <[email protected]>, 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 <[email protected]>.

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 <[email protected]>. 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.

From perl-5.005 5.005.03-7.1 in Debian 2.2 (Potato). Parsed by carta from the page's man source.