Internet Surfer 2.0/Internet Surfer 2.0 (Wayzata Technology) (1996).iso/pc/text/mac/faqs.432

Text File | 1996-02-12 | 27.8 KB | 744 lines

Frequently Asked Questions (FAQS);faqs.432




1.17) Is there a Perl profiler?

    While there isn't one included with the perl source distribution,
    various folks have written packages that allow you to do at least some
    sort of profiling.  The strategy usually includes modifying the perl
    debugger to handle profiling.  Authors of these packages include

    Wayne Thompson         <[e-mail]>
    Ray Lischner         <[e-mail]>
    Kresten Krab Thorup     <[e-mail]>

    The original articles by these folks containing their
    profilers are available on convex.com in
    /pub/perl/information/profiling.shar via anon ftp.


1.18) Is there a yacc for Perl?

    Yes!! It's a version of Berkeley yacc that outputs Perl code instead
    of C code!  You can get this from ftp.sterling.com [192.124.9.1] in
    /local/perl-byacc1.8.1.tar.Z, or send the author mail for details.


1.19) How can I use curses with perl?

    One way is to build a curseperl binary by linking in your C curses
    library as described in the usub subdirectory of the perl sources.
    This requires a modicum of work, but it will be reasonably fast
    since it's all in C (assuming you consider curses reasonably fast. :-)
    Programs written using this method require the modified curseperl,
    not vanilla perl, to run.  While this is something of a disadvantage,
    experience indicates that it's better to use curseperl than to
    try to roll your own using termcap directly.

    Another possibility is to use Henk Penning's cterm package, a curses
    emulation library written in perl.  cterm is actually a separate
    program with which you communicate via a pipe.  It is available from
    ftp.cs.ruu.nl [131.211.80.17] via anonymous ftp. in the directory
    pub/PERL.  You may also acquire the package via email in compressed,
    uuencoded form by sending a message to [e-mail]
    containing these lines:

    begin
    send PERL/cterm.shar.Z
    end

    See the question on retrieving perl via mail for more information on
    how to get retrieve other items of interest from the mail server
    there.


1.20) How can I use X with Perl?

    Right now, you have several choices.  You can wait for perl5, use
    the WAFE or STDWIN packages, or try to make your own usub bindings.

    Perl5 is anticipated to be released with bindings for X, called
    guiperl.  An exciting prototype for this, written by Jon Biggar
    <[e-mail]>, Larry's *other* brother-in-law and officemate,
    is already up and running inside of Netlabs.  This program addresses
    the same dynamic gui-building problem space as does tcl/tk.

    If you can't wait or don't think that guiperl will do what you want,
    a stab at Motif bindings was begun by Theodore C. Law
    <[e-mail]> area.  His article about this is
    on convex.com in /pub/perl/info/motif for anon ftp.

    STDWIN is a library written by Guido van Rossum <[e-mail]>
    (author of the Python programming language) that is portable
    between Mac, Dos and X11.  One could write a Perl agent to
    speak to this STDWIN server.

    WAFE is a package that implements a symbolic interface to the Athena
    widgets (X11R5). A typical Wafe application consists in our framework
    of two parts: the front-end (we call it Wafe for Widget[Athena]front
    end) and an application program running typically as separate process.
    The application program can be implemented in an arbitrary programming
    language and talks to the front-end via stdio.  Since Wafe (the
    front-end) was developed using the extensible TCL shell (cite John
    Ousterhout), an application program can dynamically submit requests to
    the front-end to build up the graphical user interface; the
    application can even down-load application specific procedures into
    the front-end.  The distribution contains sample application programs
    in Perl, GAWK, Prolog, TCL, and C talking to the same Wafe binary.
    Many of the demo applications are implemented in Perl.  Wafe 0.9 can
    be obtained via anonymous ftp from
    ftp.wu-wien.ac.at:pub/src/X11/wafe-0.9.tar.Z
    (for people without name server: the ip address is 137.208.3.5)


1.21) What is perl4?  What is perl5?

    The answer to what is perl4 is nearly anything you might otherwise
    program in shell or C.  The answer to what is perl5 is basically
    Perl: the Next Generation.  In fact, it's essentially a complete
    rewrite of perl from the bottom up, and back again.

    Larry gave a talk on perl5 at a Bay LISA meeting as well as at the
    most recent USENIX LISA conference in Long Beach in which he timorously
    admitted that perl5 might possibly be beta released in early 1993.
    He enumerated some of the following features.  Note that not only have
    not all these been implemented yet, the ones further down the list
    might well not get done at all.

    a faster, tighter, more flexible interpreter
    very easy GUI Perl applications using X bindings ("guiperl")
    embeddable Perl code in C code: cc prog.c -lperl
    multiple coresident perl interpreters:
        perhaps threading and/or coroutines
    named argument passing:
        some_func( OC => $red, TOF => "\f");
    recursive lists:
        [a, b, [c, d], e] has 4 elts, the 3rd being itself a list
    typed pointers and generalized indirection:
        like @{$aptr} or &{$fptr} or &{ $table[$index] . "func" }().
    merging of list operator and function calling syntax:
        split /pat/, $string;
    subroutines without &'s:   myfunc($arg);
    generalization of dbm binding for assoc arrays to handle
        any generic fetch/store/open/close/flush package.
        (thus allowing both dbm and gdbm at once)
    object oriented programming:
        STDOUT->flush(1);
        give dog $bone;
    lexical scoping
    dynamic loading of C libraries for systems that can
    byte-compiled code for speed and maybe security

    It's tempting to want this stuff soon, since the sooner it comes
    out the sooner we can all build really cool applications.  But the
    longer Larry works on it, the more items from this list will actually
    get done, and the more robust the release will be.  So let's not
    ask him about it too often.


1.22) How does Perl compare with languages like REXX or TCL?

    REXX is an interpreted programming language first seen on IBM systems,
    and TCL is John Ousterhout's embeddable command language.  TCL's most
    intriguing feature for many people is the tcl/tk toolset that allows
    for interpreted X-based tools.

    To avoid any flamage, if you really want to know the answer to this
    question, probably the best thing to do is try to write equivalent
    code to do a set of tasks.  All three have their own newsgroups in
    which you can learn about (but hopefully not argue about) these
    languages.

    To find out more about these or other languages, you might also check
    out David Muir Sharnoff <[e-mail]>'s posting on "Catalog of
    compilers, interpreters, and other language tools" which he posts to
    comp.lang.misc, comp.sources.d, comp.archives.admin, and the
    news.answers newsgroups.  It's a comprehensive treatment of many
    different languages.  (Caveat lector: he considers Perl's syntax
    "unappealing".)   This list is archived on convex.com in
    /pub/perl/info/lang-survey.shar .


1.23) Is it a Perl program or a Perl script?

    Certainly. :-)

    Current UNIX parlance holds that anything interpreted
    is a script, and anything compiled into native machine
    code is a program.  However, others hold that a program
    is a program is a program: after all, one seldom discusses
    scripts written in BASIC or LISP.  Larry considers it
    a program if it's set in stone and you can't change it,
    whereas if you go in and hack on it, then it's a script.

    But doesn't really matter.  The terms are generally
    interchangeable today.


1.24) What's the difference between "Perl" and "perl"?

     32 :-)  [  ord('p') - ord('P')  ]

     Larry now uses "Perl" to signify the language proper and "perl" the
     implementation of it, i.e. the current interpreter.  Hence my quip
     that "Nothing but perl can parse Perl."

     On the other hand, the aesthetic value of casewise parallelism
     in "awk", "sed", and "perl" as much require the lower-case
     version as "C", "Pascal", and "Perl" require the
     upper-case version.  It's also easier to type "Perl" in
     typeset print than to be constantly switching in Courier. :-)

     In other words, it doesn't matter much, especially if all
     you're doing is hearing someone talk about the language;
     case is hard to distingish aurally.


1.25) What companies use or ship Perl?

    At this time, the known list of companies that ship Perl includes at
    least the following:

    BSDI
    Comdisco Systems
    CONVEX Computer Corporation
    Dell
    Integraph
    Kubota Pacific (/usr/contrib)
    Netlabs

    Many other companies use Perl internally for purposes of tools
    development, systems administration, installation scripts, and test
    suites.  Rumor has it that the large workstation vendors (the TLA set)
    are seriously looking into shipping Perl with their standard systems
    "soon".

    People with support contracts with their vendors are actively
    encouraged to submit enhancement requests that Perl be shipped
    as part of their standard system.  It would, at the very least,
    reduce the FTP load on the Internet. :-)


1.26) Is there commercial, 3rd-party support for Perl?

    No.  Although perl is included in the GNU distribution, at last check,
    Cygnus does not offer support for it.  However, it's unclear whether
    they've ever been offered sufficient financial incentive to do so.

    On the other hand, you do have comp.lang.perl as a totally gratis
    support mechanism.  As long as you ask "interesting" questions,
    you'll probably get plenty of help. :-)

1.27) Where can I get a list of the JAPH signature quotes?

    These are the "just another perl hacker" signatures that
    some people sign their postings with.  About 100 of the
    of the earlier ones are on convex.com in /pub/perl/info/japh.

1.28) Where can I get a list of Larry Wall witticisms?

    Over a hundred quips by Larry, from postings of his or source code,
    can be found on convex.com in /pub/perl/info/lwall-quotes.

1.29) Is there a pretty-printer for Perl?

    That depends on what you mean.  If you want something
    that works like vgrind on Perl programs, then the answer
    is "yes, nearly".  Here's a vgrind entry for perl:

    PERL|perl|Perl:\
        :pb=(^\d?sub\d\p\d?|\{):\
        :bb={:be=}:cb=#:ce=$:sb=":se=\e":lb=':\
        :le=\e':tl:\
        :id=_:\
        :kw=\
        if for foreach unless until while continue else elsif \
        do eval require \
        die exit \
        defined delete reset \
        goto last redo next dump \
        local undef return  \
        write format  \
        sub package

    It doesn't actually do everything right; in particular,
    things like $#, $', s#/foo##, and $foo'bar all confuse it.

    If what you mean is whether there is a program that will
    reformat the program much as indent(1) will do for C, then
    the answer is no.  The complex feedback between the scanner
    and the parser (as in the things that confuse vgrind) make
    it challenging to write at best to write a stand-alone C parser.
--
    Tom Christiansen      [e-mail]      convex!tchrist

    California is a fine place to live -- if you happen to be an orange.
            -- Fred Allen
--
    Tom Christiansen      [e-mail]      convex!tchrist

    As far as we know, our computer has never had an undetected error.
            -- Weisert
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From: [e-mail] (Tom Christiansen)
Newsgroups: comp.lang.perl,news.answers
Subject: comp.lang.perl FAQ (part 2 of 2)
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Date: 30 Nov 92 13:04:40 GMT
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Archive-name: perl-faq/part2
Version: $Id: perl-tech,v 1.2 92/11/30 05:22:44 tchrist Exp Locker: tchrist $

This posting contains answers to the following techical questions
regarding Perl:

2.1) What are all these $@*%<> signs and how do I know when to use them?
2.2) Why don't backticks work as they do in shells?
2.3) How come Perl operators have different precedence than C operators?
2.4) How come my converted awk/sed/sh script runs more slowly in Perl?
2.5) How can I call my system's unique C functions from Perl?
2.6) Where do I get the include files to do ioctl() or syscall()?
2.7) Why doesn't "local($foo) = <FILE>;" work right?
2.8) How can I detect keyboard input without reading it?
2.9) How can I make an array of arrays or other recursive data types?
2.10) How can I quote a variable to use in a regexp?
2.11) Why do setuid Perl scripts complain about kernel problems?
2.12) How do I open a pipe both to and from a command?
2.13) How can I change the first N letters of a string?
2.14) How can I manipulate fixed-record-length files?
2.15) How can I make a file handle local to a subroutine?
2.16) How can I extract just the unique elements of an array?
2.17) How can I call alarm() or usleep() from Perl?
2.18) How can I test whether an array contains a certain element?
2.19) How can I do an atexit() or setjmp()/longjmp() in Perl?
2.20) Why doesn't Perl interpret my octal data octally?
2.21) How do I sort an associative array by value instead of by key?
2.22) How can I capture STDERR from an external command?
2.23) Why doesn't open return an error when a pipe open fails?
2.24) How can I compare two date strings?
2.25) What's the fastest way to code up a given task in perl?
2.26) How can I know how many entries are in an associative array?
2.27) Why can't my perl program read from STDIN after I gave it ^D (EOF) ?
2.28) Do I always/never have to quote my strings or use semicolons?
2.29) How can I translate tildes in a filename?
2.30) How can I convert my shell script to Perl?
2.31) What is variable suicide and how can I prevent it?
2.32) Can I use Perl regular expressions to match balanced text?
2.33) Can I use Perl to run a telnet or ftp session?
2.34) What does "Malformed command links" mean?
2.35) How can I set up a footer format to be used with write()?
2.36) Why does my Perl program keep growing in size?


2.1) What are all these $@*%<> signs and how do I know when to use them?

    Those are type specifiers: $ for scalar values, @ for indexed arrays,
    and % for hashed arrays.  The * means all types of that symbol name
    and are sometimes used like pointers; the <> are used for inputting
    a record from a filehandle.  See the question on arrays of arrays
    for more about Perl pointers.

    Always make sure to use a $ for single values and @ for multiple ones.
    Thus element 2 of the @foo array is accessed as $foo[2], not @foo[2],
    which is a list of length one (not a scalar), and is a fairly common
    novice mistake.  Sometimes you can get by with @foo[2], but it's
    not really doing what you think it's doing for the reason you think
    it's doing it, which means one of these days, you'll shoot yourself
    in the foot; ponder for a moment what these will really do:
    @foo[0] = `cmd args`;
    @foo[2] = <FILE>;
    Just always say $foo[2] and you'll be happier.

    This may seem confusing, but try to think of it this way:  you use the
    character of the type which you *want back*.  You could use @foo[1..3] for
    a slice of three elements of @foo, or even @foo{A,B,C} for a slice of
    of %foo.  This is the same as using ($foo[1], $foo[2], $foo[3]) and
    ($foo{A}, $foo{B}, $foo{C}) respectively.  In fact, you can even use
    lists to subscript arrays and pull out more lists, like @foo[@bar] or
    @foo{@bar}, where @bar is in both cases presumably a list of subscripts.

    While there are a few places where you don't actually need these type
    specifiers, except for files, you should always use them.  Note that
    <FILE> is NOT the type specifier for files; it's the equivalent of awk's
    getline function, that is, it reads a line from the handle FILE.  When
    doing open, close, and other operations besides the getline function on
    files, do NOT use the brackets.

    Beware of saying:
    $foo = BAR;
    Which wil be interpreted as
    $foo = 'BAR';
    and not as
    $foo = <BAR>;
    If you always quote your strings, you'll avoid this trap.

    Normally, files are manipulated something like this (with appropriate
    error checking added if it were production code):

    open (FILE, ">/tmp/foo.$$");
    print FILE "string\n";
    close FILE;

    If instead of a filehandle, you use a normal scalar variable with file
    manipulation functions, this is considered an indirect reference to a
    filehandle.  For example,

    $foo = "TEST01";
    open($foo, "file");

    After the open, these two while loops are equivalent:

    while (<$foo>) {}
    while (<TEST01>) {}

    as are these two statements:

    close $foo;
    close TEST01;

    but NOT to this:

    while (<$TEST01>) {} # error
        ^
        ^ note spurious dollar sign

    This is another common novice mistake; often it's assumed that

    open($foo, "output.$$");

    will fill in the value of $foo, which was previously undefined.
    This just isn't so -- you must set $foo to be the name of a valid
    filehandle before you attempt to open it.


2.2) Why don't backticks work as they do in shells?

    Several reason.  One is because backticks do not interpolate within
    double quotes in Perl as they do in shells.

    Let's look at two common mistakes:

         $foo = "$bar is `wc $file`";  # WRONG

    This should have been:

     $foo = "$bar is " . `wc $file`;

    But you'll have an extra newline you might not expect.  This
    does not work as expected:

      $back = `pwd`; chdir($somewhere); chdir($back); # WRONG

    Because backticks do not automatically eat trailing or embedded
    newlines.  The chop() function will remove the last character from
    a string.  This should have been:

      chop($back = `pwd`); chdir($somewhere); chdir($back);

    You should also be aware that while in the shells, embedding
    single quotes will protect variables, in Perl, you'll need
    to escape the dollar signs.

    Shell: foo=`cmd 'safe $dollar'`
    Perl:  $foo=`cmd 'safe \$dollar'`;


2.3) How come Perl operators have different precedence than C operators?

    Actually, they don't; all C operators have the same precedence in Perl as
    they do in C.  The problem is with a class of functions called list
    operators, e.g. print, chdir, exec, system, and so on.  These are somewhat
    bizarre in that they have different precedence depending on whether you
    look on the left or right of them.  Basically, they gobble up all things
    on their right.  For example,

    unlink $foo, "bar", @names, "others";

    will unlink all those file names.  A common mistake is to write:

    unlink "a_file" || die "snafu";

    The problem is that this gets interpreted as

    unlink("a_file" || die "snafu");

    To avoid this problem, you can always make them look like function calls
    or use an extra level of parentheses:

    (unlink "a_file") || die "snafu";
    unlink("a_file")  || die "snafu";

    Sometimes you actually do care about the return value:

    unless ($io_ok = print("some", "list")) { }

    Yes, print() return I/O success.  That means

    $io_ok = print(2+4) * 5;

    returns 5 times whether printing (2+4) succeeded, and
    print(2+4) * 5;
    returns the same 5*io_success value and tosses it.

    See the Perl man page's section on Precedence for more gory details,
    and be sure to use the -w flag to catch things like this.


2.4) How come my converted awk/sed/sh script runs more slowly in Perl?

    The natural way to program in those languages may not make for the fastest
    Perl code.  Notably, the awk-to-perl translator produces sub-optimal code;
    see the a2p man page for tweaks you can make.

    Two of Perl's strongest points are its associative arrays and its regular
    expressions.  They can dramatically speed up your code when applied
    properly.  Recasting your code to use them can help a lot.

    How complex are your regexps?  Deeply nested sub-expressions with {n,m} or
    * operators can take a very long time to compute.  Don't use ()'s unless
    you really need them.  Anchor your string to the front if you can.

    Something like this:
    next unless /^.*%.*$/;
    runs more slowly than the equivalent:
    next unless /%/;

    Note that this:
    next if /Mon/;
    next if /Tue/;
    next if /Wed/;
    next if /Thu/;
    next if /Fri/;
    runs faster than this:
    next if /Mon/ || /Tue/ || /Wed/ || /Thu/ || /Fri/;
    which in turn runs faster than this:
    next if /Mon|Tue|Wed|Thu|Fri/;
    which runs *much* faster than:
    next if /(Mon|Tue|Wed|Thu|Fri)/;

    There's no need to use /^.*foo.*$/ when /foo/ will do.

    Remember that a printf costs more than a simple print.

    Don't split() every line if you don't have to.

    Another thing to look at is your loops.  Are you iterating through
    indexed arrays rather than just putting everything into a hashed
    array?  For example,

    @list = ('abc', 'def', 'ghi', 'jkl', 'mno', 'pqr', 'stv');

    for $i ($[ .. $#list) {
        if ($pattern eq $list[$i]) { $found++; }
    }

    First of all, it would be faster to use Perl's foreach mechanism
    instead of using subscripts:

    foreach $elt (@list) {
        if ($pattern eq $elt) { $found++; }
    }

    Better yet, this could be sped up dramatically by placing the whole
    thing in an associative array like this:

    %list = ('abc', 1, 'def', 1, 'ghi', 1, 'jkl', 1,
         'mno', 1, 'pqr', 1, 'stv', 1 );
    $found += $list{$pattern};

    (but put the %list assignment outside of your input loop.)

    You should also look at variables in regular expressions, which is
    expensive.  If the variable to be interpolated doesn't change over the
    life of the process, use the /o modifier to tell Perl to compile the
    regexp only once, like this:

    for $i (1..100) {
        if (/$foo/o) {
        &some_func($i);
        }
    }

    Finally, if you have a bunch of patterns in a list that you'd like to
    compare against, instead of doing this:

    @pats = ('_get.*', 'bogus', '_read', '.*exit', '_write');
    foreach $pat (@pats) {
        if ( $name =~ /^$pat$/ ) {
        &some_func();
        last;
        }
    }

    If you build your code and then eval it, it will be much faster.
    For example:

    @pats = ('_get.*', 'bogus', '_read', '.*exit', '_write');
    $code = <<EOS
        while (<>) {
            study;
EOS
    foreach $pat (@pats) {
        $code .= <<EOS
        if ( /^$pat\$/ ) {
            &some_func();
            next;
        }
EOS
    }
    $code .= "}\n";
    print $code if $debugging;
    eval $code;



2.5) How can I call my system's unique C functions from Perl?

    If these are system calls and you have the syscall() function, then
    you're probably in luck -- see the next question.  For arbitrary
    library functions, it's not quite so straight-forward.  While you
    can't have a C main and link in Perl routines, if you're
    determined, you can extend Perl by linking in your own C routines.
    See the usub/ subdirectory in the Perl distribution kit for an example
    of doing this to build a Perl that understands curses functions.  It's
    neither particularly easy nor overly-documented, but it is feasible.


2.6) Where do I get the include files to do ioctl() or syscall()?

    These are generated from your system's C include files using the h2ph
    script (once called makelib) from the Perl source directory.  This will
    make files containing subroutine definitions, like &SYS_getitimer, which
    you can use as arguments to your function.

    You might also look at the h2pl subdirectory in the Perl source for how to
    convert these to forms like $SYS_getitimer; there are both advantages and
    disadvantages to this.  Read the notes in that directory for details.

    In both cases, you may well have to fiddle with it to make these work; it
    depends how funny-looking your system's C include files happen to be.

    If you're trying to get at C structures, then you should take a look
    at using c2ph, which uses debugger "stab" entries generated by your
    BSD or GNU C compiler to produce machine-independent perl definitions
    for the data structures.  This allows to you avoid hardcoding
    structure layouts, types, padding, or sizes, greatly enhancing
    portability.  c2ph comes with the perl distribution.  On an SCO
    system, GCC only has COFF debugging support by default, so you'll have
    to build GCC 2.1 with DBX_DEBUGGING_INFO defined, and use -gstabs to
    get c2ph to work there.

    See the file /pub/perl/info/ch2ph on convex.com via anon ftp
    for more traps and tips on this process.


2.7) Why doesn't "local($foo) = <FILE>;" work right?

    Well, it does.  The thing to remember is that local() provides an array
    context, and that the <FILE> syntax in an array context will read all the
    lines in a file.  To work around this, use:

    local($foo);
    $foo = <FILE>;

    You can use the scalar() operator to cast the expression into a scalar
    context:

    local($foo) = scalar(<FILE>);


2.8) How can I detect keyboard input without reading it?

    You should check out the Frequently Asked Questions list in
    comp.unix.* for things like this: the answer is essentially the same.
    It's very system dependent.  Here's one solution that works on BSD
    systems:

    sub key_ready {
        local($rin, $nfd);
        vec($rin, fileno(STDIN), 1) = 1;
        return $nfd = select($rin,undef,undef,0);
    }

    A closely related question is how to input a single character from the
    keyboard.  Again, this is a system dependent operation.  The following
    code that may or may not help you:

    $BSD = -f '/vmunix';
    if ($BSD) {
        system "stty cbreak </dev/tty >/dev/tty 2>&1";
    }
    else {
        system "stty", '-icanon',
        system "stty", 'eol', "\001";
    }

    $key = getc(STDIN);

    if ($BSD) {
        system "stty -cbreak </dev/tty >/dev/tty 2>&1";
    }
    else {
        system "stty", 'icanon';
        system "stty", 'eol', '^@'; # ascii null
    }
    print "\n";

    You could also handle the stty operations yourself for speed if you're
    going to be doing a lot of them.  This code works to toggle cbreak
    and echo modes on a BSD system:

    sub set_cbreak { # &set_cbreak(1) or &set_cbreak(0)
    local($on) = $_[0];
    local($sgttyb,@ary);
    require 'sys/ioctl.ph';
    $sgttyb_t   = 'C4 S' unless $sgttyb_t;  # c2ph: &sgttyb'typedef()

    ioctl(STDIN,&TIOCGETP,$sgttyb) || die "Can't ioctl TIOCGETP: $!";

    @ary = unpack($sgttyb_t,$sgttyb);
    if ($on) {
        $ary[4] |= &CBREAK;
        $ary[4] &= ~&ECHO;
    } else {
        $ary[4] &= ~&CBREAK;
        $ary[4] |= &ECHO;
    }
    $sgttyb = pack($sgttyb_t,@ary);

    ioctl(STDIN,&TIOCSETP,$sgttyb) || die "Can't ioctl TIOCSETP: $!";
    }

    Note that this is one of the few times you actually want to use the
    getc() function; it's in general way too expensive to call for normal
    I/O.  Normally, you just use the <FILE> syntax, or perhaps the read()
    or sysread() functions.

    For perspectives on more portable solutions, use anon ftp to retrieve
    the file /pub/perl/info/keypress from convex.com.


2.9) How can I make an array of arrays or other recursive data types?

    Remember that Perl isn't about nested data structures (actually,
    perl0 ..  perl4 weren't, but maybe perl5 will be, at least
    somewhat).  It's about flat ones, so if you're trying to do this, you
    may be going about it the wrong way or using the wrong tools.  You
    might try parallel arrays with common subscripts.