Perl for VMS

This page refers to our old VMS system Perl installation (back in 1995). As I am pleased to announce the resurrection of OpenVMS, you can expect the current Perl version to be implemented on our new server soon.

You can now use Perl 5.001 on VMS from your commandline. You can even link Perl to your images (by PERLSHR/SHARE), but use also the proper optionsfile (PUBLIC:PERLSHR_ATTR/OPT)!

To define all needed logicals and the symbol PERL itself, you should invoke @PUBLIC:STARTUP_PERL before starting Perl. There is online-help available through WWW - try the PERL - Manpages!

perl - Practical Extraction and Report Language

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.

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".

* 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.

* Embeddible 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.

* 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 just for autoloading.

* Regular expression enhancements
You can now specify non-greedy 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.

Ok, that's definitely enough hype..

Back to me!

Page origins from: 13-Apr-1995
Last update: 13-Apr-2002