Perl FAQ, Part 1:
General Information and Availability

1.1) What is Perl?
1.2) What are perl4 and perl5, are there any differences?
1.3) What features does perl5 provide over perl4?
1.4) Where can I get docs on perl5?
1.5) Will perl5 break my perl4 scripts?
1.6) When will Perl stabilize?
1.7) What's the difference between "perl" and "Perl"?
1.8) Is it a perl program or a perl script?
1.9) Is perl difficult to learn?
1.10) Should I program everything in perl?
1.11) How does perl compare with other scripting languages, like Tcl, Python or REXX?
1.12) Where can I get Perl over the Internet (FTP)?
1.13) How can I get Perl via email?
1.14) How can I get Perl via UUCP?
1.15) Are there other ways of getting perl?
1.16) Has perl been ported to machine FOO?
1.17) How do I get perl to compile on Solaris?
1.18) How do I get perl to compile on a NeXT?
1.19) What extensions are available for Perl and where can I get them?
1.20) What is dbperl and where can I get it?
1.21) Which DBM should I use?
1.22) Is there an SNMP aware perl?
1.23) Is there an ISO or ANSI certified version of Perl?

1.1) What is Perl?

Perl is a compiled scripting language written by Larry Wall*.

Here's the beginning of the description from the perl(1) man page:

Perl is an interpreted 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). It 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 hash tables used by 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 associative arrays (where dbm is available). 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. OK, enough hype.

1.2) What are perl4 and perl5, are there any differences?

Perl4 and perl5 are different versions of the language. Perl4 was the previous release, and perl5 is ``Perl: The Next Generation.'' Perl5 is, essentially, a complete rewrite of the perl source code from the ground up. It has been modularized, object oriented, tweaked, trimmed, and optimized until it almost doesn't look like the old code. However, the interface is mostly the same, and compatibility with previous releases is very high.

1.3) What features does perl5 provide over perl4?

If you get the newest source (from any of the main FTP sites), you will find a directory full of man pages (possibly to be installed as section 1p and 3pm) that discuss the differences, new features, old incompatibilies and much more. Here, however, are some highlights as to the new features and old incompatibilities. (Thanks to Tom Christiansen* for this section)

1.4) Where can I get docs on perl5?

The complete perl documentation is available with the Perl distribution, or can be accessed from the following sites. Note that the PerlDoc ps file is 240 pages long!!
Marked Up (HTML) format:                       (Europe)
PostScript:  (Europe)  (Europe)  (Oz)
        unable to access as of 7/15/95
TeXinfo (Emacs) Format:

1.5) Will perl5 break my perl4 scripts?

In general, no. However, certain bad old practices have become highly frowned upon. The following are the most important of the known incompatibilities between perl4 and perl5. See perltrap(1) for more details.

1.6) When will Perl stabilize?

When asked at what point the Perl code would be frozen, Larry answered:
Part of the redesign of Perl is to allow us to more or less freeze the language itself. It won't totally freeze, of course, but I think the rate of change of the core of the language is asymptotically approaching 0. In fact, as time goes on, now that we have an official extension mechanism, some of the things that are currently in the core of the language may move out (transparently) as extensions. This has already happened to dbmopen().

I've also been continuously reminding myself of what Henry Spencer calls ``second system syndrome'', in which everything under the sun gets added, resulting in a colossal kludge, like OS 360. You'll find that the new features in Perl 5 are all pretty minimalistic. The object-oriented features in particular added only one new piece of syntax, a C++-style method call.

The whole idea behind Perl is to be a fast text-processing, system-maintenance, zero-startup time language. If it gets to be so large and complicated that it isn't fast-running and easy to use, it won't be to anyone's benefit.
My motto from the start has been, ``If it ain't broke, don't fix it.'' I've been trying very hard not to remove those features from Perl that make it what it is. At the same time, a lot of streamlining has gone into the syntax. The new yacc file is about half the size of the old one, and the number of official reserved words has been cut by 2/3. All built-in functions have been unified (dualified?) as either list operators or unary operators.
I really like a lot of the features in Perl, but in order for Perl to be useful on a long term basis, those features have to stay put. I bought the Camel book less than a year ago and it sounds like within another year it will be obsolete.
The parts of Perl that the Camel book covers have not changed all that much. Most old scripts still run. Many scripts from Perl version 1.0 still run. We'll certainly be revising the Camel, but the new man pages are split up such that it's pretty easy to ferret out the new info when you want it.

We did break a few misfeatures in going to Perl 5. It seemed like the first and last chance to do so. There's a list of the incompatibilities in the documentation.

Not only is it a lot of work to recompile Perl on 20+ machines periodically, but it's hard to write scripts that are useful in the long term if the guts of the language keep changing. (And if I keep having to buy new books. I keep hearing about new features of Perl 5 that aren't documented in any of the perl 5 documentation that I can find.)
I think you'll find a lot of folks who think that 4.036 has been a pretty stable platform.

Perl 5 is a special case. I've been working on it for years. (This is part of the reason 4.036 has been so stable!) There are many changes, most of them for the better, I hope. I don't expect the transition to be without pain. But that's why I stuck numbered versions out in your bin directory, so that you can upgrade piecemeal if you like. And that's why I made the -w switch warn about many of the incompatibilities.

And overriding all that, I've tried to keep it so that you don't have to know much about the new stuff to use the old stuff. You can upgrade your knowledge piecemeal too.

The extension mechanism is designed to take over most of the evolutionary role from now on. And it's set up so that, if you don't have a particular extension, you know it right up at the front.

Are there any plans to write a Perl compiler? While interpreted Perl is great for many applications, it would also be cool to be able to precompile many scripts. (Yes, I know you can undump things, but undump isn't provided with Perl and I haven't found a copy.) The creation of a perl library and dynamically-loadable modules seems like a step in that direction.
Yes, part of the design of Perl 5 was to make it possible to write a compiler for it. It could even be done as an extension module, I suppose. Anyone looking for a master's thesis topic?

In summary, almost every concern that you might think of has already been (at least) thought about. In a perfect world, every concern could be addressed perfectly. But in this world we just have to slog through.

1.7) 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 Tom's 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 distinguish aurally.

1.8) Is it a perl program or a perl script?

It depends on whether you are talking about the perl binary or something that you wrote using perl. And, actually, even this isn't necessarily true.

``Standard'' UNIX terminology is (roughly) this: programs are compiled into machine code once and run multiple times, scripts are translated (by a program) each time they are used. However, some say that a program is anything written which is executed on a computer system. Larry considers it a program if it is set in stone and you can't change it, whereas if you can go in and hack at it, it's a script. Of course, if you have the source code, that makes just about anything a script. ;)

In general, it probably doesn't really matter. The terms are used interchangeably. If you particularly like one or the other, use it. If you want to call yourself a perl programmer, call them programs. If you want to call yourself a perl scripter, call them scripts. Randal* and I (at least) will call them hacks. (See question 2.10 ;)

Larry says that a script is what you give an actor, but a program is what you give an audience.

1.9) Is perl difficult to learn?

Not at all. Many people find Perl extremely easy to learn. There are at least three main reasons for this.

The first reason is that most of Perl has been derived from standard utilities, tools, and languages that you are (probably) already familiar with. If you have any knowledge of the C programming language and standard C library, the Unix Shell, sed and awk, Perl should be simple and fun for you to learn.

The second reason that Perl is easy to learn is that you only have to know a very small subset of Perl to be able to get useful results. In fact, once you can master

    print "Hello, world\n";
you can start writing Perl scripts. In fact, you will probably never have to (or be able to) know everything about Perl. As you feel the need or desire to use more sophisticated features (such as C structures or networking), you can learn these as you go. The learning curve for Perl is not a steep one, especially if you have the headstart of having a background in UNIX. Rather, its learning curve is gentle and gradual, but it is admittedly rather long.

The third reason is that you can get immediate results from your scripts. Unlike a normal compiled language (like C or Pascal, for example), you don't have to continually recompile your program every time you change one little thing. Perl allows you to experiment and test/debug quickly and easily. This ease of experimentation flattens the learning curve even more.

If you don't know C or UNIX at all, it'll be a steeper learning curve, but what you then learn from Perl will carry over into other areas, like using the C library, UNIX system calls, regular expressions, and associative arrays, just to name a few. To know Perl is to know UNIX, and vice versa.

1.10) Should I program everything in Perl?

Most definitely. In fact, you should delete the binaries for sed, awk, cc, gcc, grep, rm, ls, cat... well, just delete your /bin directory.

But seriously, of course you shouldn't. As with any job, you should use the appropriate tool for the task at hand. Just because a hammer will put screws into a piece of board, you probably don't want to do that.

While it's true that the answer to the question ``Can I do (some arbitrary task) in Perl?'' is almost always ``yes'', that doesn't mean this is necessarily a good thing to do. For many people, Perl serves as a great replacement for shell programming. For a few people, it also serves as a replacement for most of what they'd do in C. But for some things, Perl just isn't the optimal choice.

1.11) How does Perl compare with other scripting languages, like Tcl, Python or REXX?

REXX is an interpreted programming language first seen on IBM systems. Python is an interpreted programming language by Guido van Rossum*. TCL is John Ousterhout*'s embeddable command language, designed just for embedded command extensions, but lately used for larger applications. TCL's most intriguing feature for many people is the tcl/tk toolset that allows for interpreted X-based tools. Others use it for its ``expect'' extension.

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*'s posting ``Catalog of Compilers, Interpreters, and Other Language Tools'' which he posts to comp.lang.misc, comp.sources.d, comp.archives.admin, and news.answers newsgroups. It's a comprehensive treatment of many different languages. (Caveat lector: he considers Perl's syntax ``unappealing''.)

1.12) How can I get Perl over the Internet?

Perl is available from any comp.sources.misc archive. You can use an archie server (see the alt.sources FAQ in news.answers) to find these if you want.

Version 4:
Volume  Issues  Patchlevel and Notes
------  ------  ------------------------------------------------
  18    19-54   Patchlevel 3, Initial posting.
  20    56-62   Patches 4-10

Version 5:
Volume  Issues  Patchlevel and Notes
------  ------  -----------------------------------------------
  45    64-128  Initial Posting, patchlevel 0.
Since 1993, a number of archives have sprung up specifically for Perl and Perl related items. Larry maintains the official distribution site (for both perl4.036 and perl5) at netlabs. Probably the largest archive is at the University of Florida. In order of probability these sites will have the sources.

Site    Directory and notes                         IP
---------------------------------------------       -------

North America:               
        not current as of 7/15/95          
        not current as of 7/15/95        
        not current as of 7/15/95                



South America (mirror of           

If there is a site in Asia or Japan, please tell us about it. Thanks!

You can also retrieve perl via non-ftp methods:   

1.13) How can I get Perl via Email?

The following is a list of known ftpmail sites. Please attempt to use the site closest to you with the ftp archive closest to it. Many of these sites already have perl on them. For information on how to use one of these sites, send email containing the word ``help'' to the address.

    United States:
	New Jersey:
	North Carolina:


Henk P Penning* suggests that if you are in Europe you should try the following (if you are in Germany or the UK, you should probably use one of the servers listed above):
    Email: Send a message to '' containing:
     path your_email_address
     send help
     send PERL/perl5.0/INDEX
    The path-line may be omitted if your message contains a normal
    From:-line.  You will receive a help-file and an index of the
    directory that contains the Perl stuff.

If all else fails, mail to Larry usually suffices.

1.14) How can I get Perl via UUCP?

There currently is no way of getting Perl via UUCP. If anyone knows of a way, please contact me. The OSU site has discontinued the service.

1.15) Are there other ways of getting perl?

Another possibility is to use UUNET, although they charge you for it. You have been duly warned. Here's the advertisement:

Anonymous Access to UUNET's Source Archives

UUNET now provides access to its extensive collection of UNIX related sources to non- subscribers. By calling 1-900-468-7727 and using the login ``uucp'' with no password, anyone may uucp any of UUNET's on line source collection. Callers will be charged 40 cents per minute. The charges will appear on their next tele- phone bill.

The file uunet!/info/help contains instructions. The file uunet!/index//ls-lR.Z contains a complete list of the files available and is updated daily. Files ending in Z need to be uncompressed before being used. The file uunet!~/compress.tar is a tar archive containing the C sources for the uncompress program.

This service provides a cost effective way of obtaining current releases of sources without having to maintain accounts with UUNET or some other service. All modems connected to the 900 number are Telebit T2500 modems. These modems support all standard modem speeds including PEP, V.32 (9600), V.22bis (2400), Bell 212a (1200), and Bell 103 (300). Using PEP or V.32, a 1.5 megabyte file such as the GNU C compiler would cost $10 in con- nect charges. The entire 55 megabyte X Window system V11 R4 would cost only $370 in connect time. These costs are less than the official tape distribution fees and they are available now via modem.

UUNET Communications Services
3110 Fairview Park Drive, Suite 570
Falls Church, VA 22042
+1 703 876 5050 (voice)
+1 703 876 5059 (fax)

1.16) Has perl been ported to machine FOO?

Perl runs on virtually all Unix machines simply by following the hints file and instructions in the Configure script. This auto-configuration script allows Perl to compile on a wide variety of platforms by modifying the machine specific parts of the code. For most Unix systems, or VMS systems for v5 perl, no porting is required. Try to compile Perl on your machine. If you have problems, examine the README file carefully. If all else fails, send a message to comp.lang.perl.misc and crosspost to comp.sys.[whatever], there's probably someone out there that has already solved your problem and will be able to help you out.

Perl4.036 has been ported to many non-Unix systems, although currently there are only a few (beta) v5 ports. All of the following are mirrored at The following are the (known) official distribution points. Please contact the porters directly (when possible) in case of questions on these ports.

1.17) How do I get Perl to compile on Solaris?

The following directions are for perl, version 4. Perl, version 5, should compile more easily. If not, send mail to The Perl Porters Mailing List (

John Lees* reports:

I have built perl on Solaris 2.1, 2.2 beta, and 2.2 FCS. Take /usr/ucb out of your path and do not use any BSD/UCB libraries. Only -lsocket, -lnsl, and -lm are needed. You can use the hint for Solaris 2.0, but the one for 2.1 is wrong. Do not use vfork. Do not use -I/usr/ucbinclude. The result works fine for me, but of couse does not support a couple of BSDism's.

Casper H.S. Dik* reports

You must remove all the references to /usr/ucblib AND /usr/ucbinclude. And ignore the Solaris_2.1 hints. They are wrong. The undefining of vfork() probably has to do with the confusion it gives to the compilers. If you use cc, you mustn't compile util.c/tutil.c with -O. I only used the following libs: -lsocket -lnsl -lm (there is a problem with -lmalloc)

Michael D'Errico* reports:

If you are using Solaris 2.x, the signal handling is broken. If you set up a signal handler such as 'ripper' it will be forgotten after the first time the signal is caught. To fix this, you need to recompile Perl. Just add '#define signal(x,y) sigset((x),(y))' after the '#include ' directive in each file that it occurs, then make it again.

1.18) How do I get Perl to compile on a Next?

According to Andreas Koenig*, under NeXTstep 3.2, both perl4.036 and perl5.000 compile with the supplied hints file.

However, Bill Eldridge* provides this message to help get perl4.036 on NeXTstep 3.0 to work:

To get perl to compile on NeXTs, you need to combine the ANSI and BSD headers:

    cd /usr/include
    mkdir ansibsd
    cd ansibsd
    ln -s ../ansi
    ln -s ../bsd

Then, follow the configuration instructions for NeXTs, replacing all mention of -I/usr/include/ansi or -I/usr/include/bsd with -I/usr/include/ansibsd.

1.19) What extensions are available from Perl and where can I get them?

Some of the more popular extensions include those for windowing, graphics, or data base work. Most of the major sites contain an archive of the extensions, usually in the ext directory. Since the list of available extensions changes so often, I have opted to list only the sites and directories, not the individual extensions, please check the closest archive for more information

1.20) What is dbperl and where can I get it?

Many database-oriented extensions to Perl have been written. Basically, these use the usub mechanism (see the usub/ subdirectory) in the source distribution) to link in a database library, allowing embedded calls to Informix, Ingres, Interbase, Oracle and Sybase.

Here are the authors of the various extensions:

What            Target DB       Who
--------        -----------     ----------------------------------------
?Infoperl       Informix        Kurt Andersen (
Ingperl         Ingres          Tim Bunce ( and Ted Lemon
Interperl       Interbase       Buzz Moschetti (
Isqlperl        Informix        William Hails
Oraperl         Oracle          Kevin Stock (
Pgperl          Postgres        Igor Metz (
*Sqlperl        Ingres          Ted Lemon (
Sybperl         Sybase          Michael Peppler (
Uniperl         Unify 5.0       Rick Wargo (

    ? Does this one still exist?
*Sqlperl appears to have been subsumed by Ingperl

Buzz Moschetti* has organized a project to create a higher level interface to allow you to write your queries in a database-independent fashion. If this type of project interests you, send mail to <> and asked to be placed on the ``perldb-interest'' mailing lists.

Here's a bit of advertising from Buzz:

Perl is an interpreted language with powerful string, scalar, and array processing features developed by Larry Wall that ``nicely bridges the functionality gap between sh(1) and C.'' Since relational DB operations are typically textually oriented, perl is particularly well-suited to manage the data flows. The C source code, which is available free of charge and runs on many platforms, contains a user-defined function entry point that permits a developer to extend the basic function set of the language. The DBperl Group seeks to exploit this capability by creating a standardized set of perl function extensions (e.g. db_fetch(), db_attach()) based on the SQL model for manipulating a relational DB, thus providing a portable perl interface to a variety of popular RDMS engines including Sybase, Oracle, Ingres, Informix, and Interbase. In theory, any DB engine that implements a dynamic SQL interpreter in its HLI can be bolted onto the perl front end with predicatable results, although at this time backends exist only for the aforementioned five DB engines.

The official archive for DBperl extensions is It's the home of the evolving DBperl API Specification. Here's an extract from the updated README there:

DBI/        The home of the DBI archive. To join the DBI mailing list
	    send your request to

DBD/        Database Drivers for the DBI ...

Oracle/      By Tim Bunce (not yet ready!)
Ingres/      By Tim Bunce (not yet started!)

mod/           Other Perl 5 Modules and Extensions ...

Sybperl/    By Michael Peppler,

perl4/         Perl 4 extensions (using the usub C interface)

   oraperl/   ORACLE 6 & 7  By Kevin Stock,
   sybperl/   SYBASE 4      By Michael Peppler,
   ingperl/   INGRES        By Tim Bunce and Ted Lemon
   isqlperl/  INFORMIX      By William Hails,
   interperl/ INTERBASE     By Buzz Moschetti,
   oraperl/   ORACLE 6 & 7  By Kevin Stock (sadly no longer on the net)
   sybperl/   SYBASE 4      By Michael Peppler,
   ingperl/   INGRES        By Tim Bunce and Ted Lemon
   isqlperl/  INFORMIX      By William Hails,
   interperl/ INTERBASE     By Buzz Moschetti,
   uniperl/   UNIFY 5.0     By Rick Wargo,
   pgperl/    POSTGRES      By Igor Metz,

   btreeperl/ NDBM perl extensions.   By John Conover,
   ctreeperl/ C-Tree perl extensions. By John Conover,
   duaperl/   X.500 Directory User Agent. By Eric Douglas.

scripts/       Perl and shell scripts

   rdb/       RDB is a perl RDBMS for ASCII files. By Walt Hobbs,
   shql/      SHQL is an interactive SQL database engine.  Written as a
		shell script, SHQL interprets SQL commands and
		manipulates flat files based on those commands. By
		Bruce Momjian, root@candle.uucp
   xbase/     Perl scripts for accessing xBase style files (dBase III)

refinfo/       Reference information

   sqlsyntax/ Yacc and lex syntax and C source code for SQL1 and SQL2
	and a draft SQL3 syntax from Jeff Fried <>+
   formats/   Details of file formats such as Lotus 1-2-3 .WK1

There are also a number of non SQL database interfaces for perl available from These include:

Directory   Target System   Authors and notes
---------   -------------   -------------------------------------------
btreeperl   NDBM extension  John Conover (
ctreeperl   CTree extension John Conover (
duaperl     X.500 DUA       Eric Douglas
rdb         RDBMS           Walt Hobbs (
shql        SQL Engine      Bruce Momjian (root@candle.uucp)

1.21) Which DBM should I use?

As shipped, Perl (version 5) comes with interfaces for several DBM packages (SDBM, old DBM, NDBM, GDBM, Berkeley DBM) that are not supplied but either come with your system are readily accessible via FTP. SDBM is guaranteed to be there. For a comparison, see AnyDBM_File(3pm) and DB_File(3pm) .

1.22) Is there an SNMP aware Perl?

snmperl was written by Guy Streeter (, and was posted in late February 1993 to comp.protocols.snmp. It can be found archived at one of two (known) places:

Location: /pub/net/snmp
       FILE -rw-rw-r--       3407  Aug 11 1992  snmperl.README
       FILE -rw-r--r--      17678  Aug 11 1992  snmperl.tar.Z

Location: /pub/perl/scripts/snmp

Here is the gist of the README:

This directory contains the source code to add callable C subroutines to perl. The subroutines implement the SNMP functions ``get'', ``getnext'', and ``set''. They use the freely-distributable SNMP package (version 1.1b) from CMU.

USE: There are four subroutines defined in the callable interface: snmp_get, snmp_next, snmp_set, and snmp_error.

snmp_get and snmp_next implement the GET and GETNEXT operations, respectively. The first two calling arguments are the hostname and Community string. The IP address of the host, as a dotted-quad ASCII string, may be used as the hostname. The rest of the calling arguments are a list of variables. See the CMU package documentation for how variables may be specified.

snmp_set also takes hostname and Community string as arguments. The remaining arguments are a list of triples consisting of variable name, variable type, and value. The variable type is a string, such as ``INTEGER'' or ``IpAddress''.

snmp_get, snmp_next, and snmp_set return a list containing alternating variables and values. snmp_get and snmp_next will simply omit non-existent variables on return. snmp_set will fail completely if one of the specified variables does not exist (or is read-only).

snmp_error will return a text string containing some error information about the most recent snmp_get|next|set call, if it had an error.

I didn't find all the places where the CMU library writes to stderr or calls exit() directly.

The changes I made to mib.c involve the formatting of variable values for return to the caller. I took out the descriptive prefix so the string contains only the value.

Enumerated types are returned as a string containing the symbolic representation followed in parentheses by the numeric.


perl and the CMU SNMP package have their own statements. Read them. The work I've done is free and clear. Just don't say you wrote it if you didn't, and don't say I wrote it if you change it.

    Guy Streeter
    April 1, 1992 (not a joke!)

1.23) Is there an ISO or ANSI certified version of Perl?

No. Larry thinks it likely that he'll be certified before perl is.

Other resources at this site: