PERL(1)          Perl Programmers Reference Guide         PERL(1)

       perl - Practical Extraction and Report Language

       ppeerrll [ --ssTTuuUU ]      [ --hhvv ] [ --VV[:configvar] ]
            [ --ccww ] [ --dd[:debugger] ] [ --DD[number/list] ]
            [ --ppnnaa ] [ --FFpattern ] [ --ll[octal] ] [ --00[octal] ]
            [ --IIdir ] [ --mm[--]module ] [ --MM[--]'module...' ]
            [ --PP ]      [ --SS ]      [ --xx[dir] ]
            [ --ii[extension] ]
            [ --ee 'command' ] [ ---- ] [ programfile ] [ argument ]...

       For ease of access, the Perl manual has been split up into
       a number of sections:

           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

       (If you're intending to read these straight through for
       the first time, the suggested order will tend to reduce
       the number of forward references.)

       By default, all of the above manpages 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

       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

       If something strange has gone wrong with your program and
       you're not sure where you should look for help, try the --ww
       switch first.  It will often point out exactly where the
       trouble is.

       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,

       Perl combines (in the author's opinion, anyway) some of
       the best features of C, sseedd, aawwkk, and sshh, so people
       familiar with those languages should have little
       difficulty with it.  (Language historians will also note
       some vestiges of ccsshh, 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

       If you have a problem that would ordinarily use sseedd or aawwkk
       or sshh, 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 sseedd and aawwkk scripts into Perl

       But wait, there's more...

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

       o 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 --ww switch!!!  Whenever you don't
            get mysterious behavior, try using --ww anyway.

       o 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.

       o 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

       o 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.

       o 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

       o 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.

       o 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.

       o 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.

       o 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 --pp or --nn

       o 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.

       o 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.

       o 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

       o 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
   for a site near you.

       o 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.

       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

       The following platforms are able to build Perl from the
       standard source code distribution available at

               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:


       The following platforms have their own source code
       distributions and binaries available via

                                       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

                                       Perl release

               Acorn RISCOS            5.005_02
               AOS                     5.002
               LynxOS                  5.004_02

       See the perlrun manpage.

       Larry Wall <>, 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 <>.

        "@INC"                 locations of perl libraries

        a2p    awk to perl translator

        s2p    sed to perl translator

       The --ww 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 --ee switches, each --ee 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 --ww switch?

       The --ww 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
       <>.  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.

       The Perl motto is "There's more than one way to do it."
       Divining how many more is left as an exercise to the

       The three principal virtues of a programmer are Laziness,
       Impatience, and Hubris.  See the Camel Book for why.

28/Mar/1999            perl 5.005, patch 03                     1