NAME
    perl - Practical Extraction and Report Language

SYNOPSIS
    perl [ -sTuU ] [ -hv ] [ -V[:*configvar*] ] [ -cw ] [
    -d[:*debugger*] ] [ -D[*number/list*] ] [ -pna ] [ -F*pattern* ]
    [ -l[*octal*] ] [ -0[*octal*] ] [ -I*dir* ] [ -m[-]*module* ] [
    -M[-]*'module...'* ] [ -P ] [ -S ] [ -x[*dir*] ] [
    -i[*extension*] ] [ -e *'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
        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
        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
        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

        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 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 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
    (previously called "associative arrays") grow as necessary to
    prevent degraded performance. Perl uses 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.

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
     "/tmp/perl-e$$"	temporary file for -e commands
     "@INC"			locations of perl libraries


SEE ALSO
     a2p	awk to perl translator

     s2p	sed to perl translator


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?

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 255
    characters, and no component of your PATH may be longer than 255
    if you use -S. A regular expression may not compile to more than
    32767 bytes internally.

    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.com>. 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.

