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Last revised: 19-Jan-1996 by Charles Bailey

The VMS port of Perl is still under development. At this time, the Perl
binaries built under VMS handle internal operations properly, for the most
part, as well as most of the system calls which have close equivalents under
VMS. There are still some incompatibilities in process handling (e.g the
fork/exec model for creating subprocesses doesn't do what you might expect
under Unix), and there remain some file handling differences from Unix. Over
the longer term, we'll try to get many of the useful VMS system services
integrated as well, depending on time and people available. Of course, if
you'd like to add something yourself, or join the porting team, we'd love to
have you!

The current sources and build procedures have been tested on a VAX using VAXC
and DECC, and on an AXP using DECC. If you run into problems with other
compilers, please let us know.

Note to DECC users: Some early versions of the DECCRTL contained a few bugs
which affect Perl performance:
    - Newlines are lost on I/O through pipes, causing lines to run together.
      This shows up as RMS RTB errors when reading from a pipe. You can
      work around this by having one process write data to a file, and
      then having the other read the file, instead of the pipe. This is
      fixed in version 4 of DECC.
    - The modf() routine returns a non-integral value for some values above
      INT_MAX; the Perl "int" operator will return a non-integral value in
      these cases. This is fixed in version 4 of DECC.
    - On the AXP, if SYSNAM privilege is enabled, the CRTL chdir() routine
      changes the process default device and directory permanently, even
      though the call specified that the change should not persist after
      Perl exited. This is fixed by DEC CSC patch AXPACRT04_061.

* Other software required

At the moment, in addition to basic VMS, you'll need two things:
   - a C compiler: VAXC, DECC, or gcc for the VAX; DECC for the AXP
   - a make tool: DEC's MMS (version 2.6 or later) or the free analog MMK
     (available from, or a standard make utility (e.g. GNU make,
     also available from
In addition, you may include socket support if you have an IP stack running
on your system. See the topic "Socket support" for more information.

* Socket support

Perl includes a number of IP socket routines among its builtin functions,
which are available if you choose to compile Perl with socket support. Since
IP networking is an optional addition to VMS, there are several different IP
stacks available, so it's difficult to automate the process of building Perl
with socket support in a way which will work on all systems.

By default, Perl is built without IP socket support. If you define the macro
SOCKET when invoking MMK, however, socket support will be included. As
distributed, Perl for VMS includes support for the SOCKETSHR socket library,
which is layered on MadGoat software's vendor-independent NETLIB interface.
This provides support for all socket calls used by Perl except the
[g|s]etnet*() routines, which are replaced for the moment by stubs which
generate a fatal error if a Perl script attempts to call one of these routines.
Both SOCKETSHR and NETLIB are available from MadGoat ftp sites, such as or

You can link Perl directly to your TCP/IP stack's library, *as long as* it
supplies shims for stdio routines which will properly handle both sockets and
normal file descriptors. This is necessary because Perl does not distinguish
between the two, and will try to make normal stdio calls such as read() and
getc() on socket file descriptors. If you'd like to link Perl directly to
your IP stack, then make the following changes:
  - In Descrip.MMS, locate the section beginning with .ifdef SOCKET, and
    change the SOCKLIB macro so that it translates to the filespec of your
    IP stack's socket library. This will be added to the RTL options file.
  - Edit the file SockAdapt.H in the [.VMS] subdirectory so that it
    includes the Socket.H, In.H, Inet.H, NetDb.H, and, if necessary,
    Errno.H header files for your IP stack, or so that it declares the
    standard TCP/IP constants and data structures appropriately. (See
    the distributed copy of SockAdapt.H for a collection of the structures
    needed by Perl itself, and [.ext.Socket]Socket.xs for a list of the
    constants used by the Socket extension, if you elect to built it.)
    You should also define any logical names necessary for your C compiler
    to find these files before invoking MM[KS] to build Perl.
  - Edit the file SockAdapt.C in the [.VMS] subdirectory so that it
    contains routines which substitute for any IP library routines
    required by Perl which your IP stack does not provide. This may
    require a little trial and error; we'll try to compile a complete
    list soon of socket routines required by Perl.

* Building Perl under VMS

Since you're reading this, presumably you've unpacked the Perl distribution
into its directory tree, in which you will find a [.vms] subdirectory below
the directory in which this file is found. If this isn't the case, then you'll
need to unpack the distribution properly, or manually edit Descrip.MMS or
the VMS Makefile to alter directory paths as necessary. (I'd advise using the
`normal' directory tree, at least for the first time through.) This
subdirectory contains several files, among which are the following:
  Config.VMS - A template Config.H set up for VMS.
  Descrip.MMS - The MMS/MMK dependency file for building Perl
  GenConfig.Pl - A Perl script to generate Config.SH retrospectively
                   from Config.VMS, since the Configure shell script which
                   normally generates Config.SH doesn't run under VMS.
  GenOpt.Com - A little DCL procedure used to write some linker options
                   files, since not all make utilities can do this easily.
  Gen_ShrFls.Pl - A Perl script which generates linker options files and
                   MACRO declarations for PerlShr.Exe.
  Makefile - The make dependency file for building Perl
  MMS2Make.Pl - A Perl script used to generate Makefile from Descrip.MMS
  PerlVMS.pod - Documentation for VMS-specific behavior of Perl
  Perly_[CH].VMS - Versions of the byacc output from Perl's grammar,
                   modified to include VMS-specific C compiler options
  SockAdapt.[CH] - C source code used to integrate VMS TCP/IP support
  Test.Com - DCL driver for Perl regression tests
  VMSish.H - C header file containing VMS-specific definitions
  VMS.C - C source code for VMS-specific routines
  VMS_Yfix.Pl - Perl script to convert Perly.[CH] to Perly_[CH].VMS
  WriteMain.Pl - Perl script to generate Perlmain.C
The [.Ext...] directories contain VMS-specific extensions distributed with
Perl. There may also be other files in [.VMS...] pertaining to features under
development; for the most part, you can ignore them. Note that packages in
[.ext.*] are not built with Perl by default; you build the ones you want
once the basic Perl build is complete (see the perlvms docs for instructions
on building extensions.)

Config.VMS and Decrip.MMS/Makefile are set up to build a version of Perl which
includes all features known to work when this release was assembled. If you
have code at your site which would support additional features (e.g. emulation
of Unix system calls), feel free to make the appropriate changes to these
files. (Note: Do not use or edit config.h in the main Perl source directory;
it is superseded by the current Config.VMS during the build.) You may also
wish to make site-specific changes to Descrip.MMS or Makefile to reflect local
conventions for naming of files, etc.

There are several pieces of system-specific information which become part of
the Perl Config extension. Under VMS, the data for Config are generated by the
script GenConfig.Pl in the [.VMS] subdirectory. It tries to ascertain the
necessary information from various files, or from the system itself, and
generally does the right thing. There is a list of hard-coded values at the
end of this script which specifies items that are correct for most VMS systems,
but may be incorrect for you, if your site is set up in an unusual fashion. If
you're familiar with Perl's Config extension, feel free to edit these values as
necessary. If this doesn't mean much to you, don't worry -- the information is
probably correct, and even if it's not, none of these parameters affect your
ability to build or run Perl. You'll only get the wrong answer if you ask for
it specifically from Config.

Examine the information at the beginning of Descrip.MMS for information about
specifying alternate C compilers or building a version of Perl with debugging
support. For instance, if you want to use DECC, you'll need to include the
/macro="decc=1" qualifier to MMK (If you're using make, these options are not
supported.) If you're on an AXP system, define the macro __AXP__ (MMK does
this for you), and DECC will automatically be selected.

To start the build, set default to the main source directory. Since
Descrip.MMS assumes that VMS commands have their usual meaning, and makes use
of command-line macros, you may want to be certain that you haven't defined DCL
symbols which would interfere with the build. Then, if you are using MMS or
MMK, say
$ MMS/Descrip=[.VMS] ! or MMK
(N.B. If you are using MMS, you must use version 2.6 or later; a bug in
earlier versions produces malformed cc command lines.) If you are using a
version of make, say
$ Make -f [.VMS]Makefile
Note that the Makefile doesn't support conditional compilation, is
set up to use VAXC on a VAX, and does not include socket support. You can
either edit the Makefile by hand, using Descrip.MMS as a guide, or use the
Makefile to build Miniperl.Exe, and then run the Perl script,
found in the [.VMS] subdirectory, to generate a new Makefile with the options
appropriate to your site.

If you are using MM[SK], and you decide to rebuild Perl with a different set
of parameters (e.g. changing the C compiler, or adding socket support), be
sure to say
$ MMK/Descrip=[.VMS] realclean
first, in order to remove files generated during the previous build. If
you omit this step, you risk ending up with a copy of Perl which
composed partially of old files and partially of new ones, which may lead
to strange effects when you try to run Perl.

A bug in some early versions of the DECC RTL on the AXP causes newlines
to be lost when writing to a pipe. A different bug in some patched versions
of DECC 4.0 for VAX can also scramble preprocessor output. Finally, gcc 2.7.2
has yet another preprocessor bug, which causes line breaks to be inserted
into the output at inopportune times. Each of these bugs causes
to fail, since it can't parse the preprocessor output to identify global
variables and routines. This problem is generally manifested as missing
global symbols when linking PerlShr.Exe or Perl.Exe. You can work around
it by defining the macro PIPES_BROKEN when you invoke MMS or MMK.

This will build the following files:
  Miniperl.Exe - a stand-alone version of without any extensions.
                        Miniperl has all the intrinsic capabilities of Perl,
                        but cannot make use of the DynaLoader or any
                        extensions which use XS code.
  PerlShr.Exe - a shareable image containing most of Perl's internal
                        routines and global variables. Perl.Exe is linked to
                        this image, as are all dynamic extensions, so everyone's
                        using the same set of global variables and routines.
  Perl.Exe - the main Perl executable image. It's contains the
                        main() routine, plus code for any statically linked
  PerlShr_Attr.Opt - A linker options file which specifies psect attributes
                        matching those in PerlShr.Exe. It should be used when
                        linking images against PerlShr.Exe
  PerlShr_Bld.Opt - A linker options file which specifies various things
                        used to build PerlShr.Exe. It should be used when
                        rebuilding PerlShr.Exe via MakeMaker-produced
                        Descrip.MMS files for static extensions.
  c2ph - Perl program which generates template code to access
                        C struct members from Perl.
  h2ph - Perl program which generates template code to access
                        #defined constants in a C header file from Perl,
                        using the "old-style" interface. (Largely supplanted
                        by h2xs.)
  h2xs - Perl program which generates template files for creating
                        XSUB extensions, optionally beginning with the #defined
                        constants in a C header file.
  [.lib.pod]perldoc - A Perl program which locates and displays documentation
                        for Perl and its extensions.
  [.Lib] - the Perl extension which saves configuration information
                        about Perl and your system.
  [.Lib] - The Perl extension which performs dynamic linking of
                        shareable images for extensions.
  Several subdirectories under [.Lib] containing preprocessed files or
                        site-specific files.
There are, of course, a number of other files created for use during the build.
Once you've got the binaries built, you may wish to `build' the `tidy' or
`clean' targets to remove extra files.

If you run into problems during the build, you can get help from the VMSPerl
or perl5-porters mailing lists (see below). When you report the problem,
please include the following information:
  - The version of Perl you're trying to build. Please include any
    "letter" patchlevel, in addition to the version number. If the
    build successfully created Miniperl.Exe, you can check this by
    saying '$ MCR Sys$Disk:[]Miniperl -v'. Also, please mention
    where you obtained the distribution kit; in particular, note
    whether you were using a basic Perl kit or the VMS test kit
    (see below).
  - The exact command you issued to build Perl.
  - A copy of all error messages which were generated during the build.
    Please include enough of the build log to establish the context of
    the error messages.
  - A summary of your configuration. If the build progressed far enough
    to generate Miniperl.Exe and [.Lib], you can obtain this
    by saying '$ MCR Sys$Disk:[]Miniperl "-V"' (note the "" around -V).
    If not, then you can say '$ MMK/Descrip=[.VMS] printconfig' to
    produce the summary.
This may sound like a lot of information to send, but it'll often make
it easier for someone to spot the problem, instead of having to give
a spectrum of possibilities.

* Installing Perl once it's built

Once the build is complete, you'll need to do the following:
  - Put PerlShr.Exe in a common directory, and make it world-readable.
    If you place it in a location other than Sys$Share, you'll need to
    define the logical name PerlShr to point to the image. (If you're
    installing on a VMScluster, be sure that each node is using the
    copy of PerlShr you expect [e.g. if you put PerlShr.Exe in Sys$Share,
    do they all share Sys$Share?]).
  - Put Perl.Exe in a common directory, and make it world-executable.
  - Define a foreign command to invoke Perl, using a statement like
    $ Perl == "$dev:[dir]Perl.Exe"
  - Create a world-readable directory tree for Perl library modules,
    scripts, and what-have-you, and define PERL_ROOT as a rooted logical
    name pointing to the top of this tree (i.e. if your Perl files were
    going to live in DKA1:[Util.Perl5...], then you should
      $ Define/Translation=Concealed Perl_Root DKA1:[Util.Perl5.]
    (Be careful to follow the rules for rooted logical names; in particular,
    remember that a rooted logical name cannot have as its device portion
    another rooted logical name - you've got to supply the actual device name
    and directory path to the root directory.)
  - Place the files from the [.lib...] directory tree in the distribution
    package into a [.lib...] directory tree off the root directory described
  - Most of the Perl documentation lives in the [.pod] subdirectory, and
    is written in a simple markup format which can be easily read. In this
    directory as well are pod2man and pod2html translators to reformat the
    docs for common display engines; a pod2hlp translator is under development.
    These files are copied to [.lib.pod] during the installation.
  - Define a foreign command to execute perldoc, such as
    $ Perldoc == "''Perl' Perl_Root:[lib.pod]Perldoc -t"
    This will allow users to retrieve documentation using Perldoc. For
    more details, say "perldoc perldoc".
That's it.

If you run into a bug in Perl, please submit a bug report. The PerlBug
program, found in the [.lib] directory, will walk you through the process
of assembling the necessary information into a bug report, and sending
of to the Perl bug reporting address,

* For more information

If you're interested in more information on Perl in general, consult the Usenet
newsgroups comp.lang.perl.announce and comp.lang.perl.misc. The FAQ for these
groups provides pointers to other online sources of information, as well as
books describing Perl in depth.

If you're interested in up-to-date information on Perl development and
internals, you might want to subscribe to the perl5-porters mailing list. You
can do this by sending a message to, containing
the single line
subscribe perl5-porters
This is a high-volume list at the moment (>50 messages/day).

If you're interested in ongoing information about the VMS port, you can
subscribe to the VMSperl mailing list by sending a request to (it's to a human, not a list server - this is a small
operation at the moment). And, as always, we welcome any help or code you'd
like to offer - you can send mail to or directly to
the VMSperl list at

Finally, if you'd like to try out the latest changes to VMS Perl, you can
retrieve a test distribution kit by anonymous ftp from, in
the file [.perl5], where "ppp" is the current Perl
patchlevel, and "yymmddx" is a sequence number indicating the date that
particular kit was assembled. In order to make retrieval convenient, this
kit is also available by the name Perl5_VMSTest.Zip. These test kits contain
"unofficial" patches from the perl5-porters group, test patches for important
bugs, and VMS-specific fixes and improvements which have occurred since the
last Perl release. Most of these changes will be incorporated in the next
release of Perl, but until Larry Wall's looked at them and said they're OK,
none of them should be considered official.

Good luck using Perl. Please let us know how it works for you - we can't
guarantee that we'll be able to fix bugs quickly, but we'll try, and we'd
certainly like to know they're out there.

* Acknowledgements

There are, of course, far too many people involved in the porting and testing
of Perl to mention everyone who deserves it, so please forgive us if we've
missed someone. That said, special thanks are due to the following:
  Tim Adye <>
     for the VMS emulations of getpw*()
  David Denholm <>
     for extensive testing and provision of pipe and SocketShr code,
  Mark Pizzolato <>
     for the getredirection() code
  Rich Salz <>
     for readdir() and related routines
  Richard Dyson <> and
  Kent Covert <>
     for additional testing on the AXP.
and to the entire VMSperl group for useful advice and suggestions. In addition
the perl5-porters, especially Andy Dougherty <>
and Tim Bunce <>, deserve credit for their creativity and
willingness to work with the VMS newcomers. Finally, the greatest debt of
gratitude is due to Larry Wall <>, for having the ideas which
have made our sleepless nights possible.

The VMSperl group
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