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README.vms - Configuring, building, testing, and installing perl on VMS


To configure, build, test, and install perl on VMS:

    @ Configure
    mms test
    mms install

mmk may be used in place of mms in the last three steps.


Important safety tip

The build and install procedures have changed significantly from the 5.004 releases! Make sure you read the "Configuring the Perl Build", "Building Perl", and "Installing Perl" sections of this document before you build or install. Also please note other changes in the current release by having a look at "VMS" in perldelta.

Also note that, as of Perl version 5.005 and later, an ANSI C compliant compiler is required to build Perl. VAX C is *not* ANSI compliant, as it died a natural death some time before the standard was set. Therefore VAX C will not compile Perl 5.005 or later. We are sorry about that.

If you are stuck without Compaq (formerly DEC) C consider trying Gnu C instead, though there have been no recent reports of builds using Gnu C. There is minimal support for Compaq C++ but this support is not complete; if you get it working please write to the vmsperl list (for info see "Mailing Lists").

Introduction to Perl on VMS

The VMS port of Perl is as functionally complete as any other Perl port (and as complete as the ports on some Unix systems). The Perl binaries provide all the Perl system calls that are either available under VMS or reasonably emulated. There are some incompatibilities in process handling (e.g. the fork/exec model for creating subprocesses doesn't do what you might expect under Unix), mainly because VMS and Unix handle processes and sub-processes very differently.

There are still some unimplemented system functions, and of course we could use modules implementing useful VMS system services, so if you'd like to lend a hand we'd love to have you. Join the Perl Porting Team Now!

The current sources and build procedures have been tested on a VAX using DEC C, and on an AXP using DEC C. If you run into problems with other compilers, please let us know. (Note: DEC C was renamed to Compaq C around version 6.2).

There are issues with various versions of DEC C, so if you're not running a relatively modern version, check the "DEC C issues" section later on in this document.

Other required software for Compiling Perl on VMS

In addition to VMS and DCL you will need two things:

1 A C compiler.

DEC (now Compaq) C or gcc for VMS (AXP or VAX).

2 A make tool.

DEC's MMS (v2.6 or later), or MadGoat's free MMS analog MMK (available from both work just fine. Gnu Make might work, but it's been so long since anyone's tested it that we're not sure. MMK is free though, so go ahead and use that.

Additional software that is optional for Perl on VMS

You may also want to have on hand:


A de-compressor for *.gz and *.tgz files available from a number of web/ftp sites and is distributed on the OpenVMS Freeware CD-ROM from Compaq.

For reading and writing unix tape archives (*.tar files). Vmstar is also available from a number of web/ftp sites and is distributed on the OpenVMS Freeware CD-ROM from Compaq.

A combination decompressor and archive reader/writer for *.zip files. Unzip is available from a number of web/ftp sites.

Most is an optional pager that is convenient to use with perldoc (unlike TYPE/PAGE, MOST can go forward and backwards in a document and supports regular expression searching). Most builds with the slang library on VMS. Most and slang are available from:

Patches to Perl are usually distributed as GNU unified or contextual diffs. Such patches are created by the GNU diff program (part of the diffutils distribution) and applied with GNU patch. VMS ports of these utilities are available here:

Please note that UNZIP and GUNZIP are not the same thing (they work with different formats). Many of the useful files from CPAN (the Comprehensive Perl Archive Network) are in *.tar.gz or *.tgz format (this includes copies of the source code for perl as well as modules and scripts that you may wish to add later) hence you probably want to have GUNZIP.EXE and VMSTAR.EXE on your VMS machine.

If you want to include socket support, you'll need a TCP/IP stack and either DEC C, or socket libraries. See the "Socket Support (optional)" topic for more details.

Configuring the Perl build ^

To configure perl (a necessary first step), issue the command

   @ Configure

from the top of an unpacked perl source directory. You will be asked a series of questions, and the answers to them (along with the capabilities of your C compiler and network stack) will determine how perl is custom built for your machine.

If you have multiple C compilers installed, you'll have your choice of which one to use. Various older versions of DEC C had some caveats, so if you're using a version older than 5.2, check the "DEC C Issues" section.

If you have any symbols or logical names in your environment that may interfere with the build or regression testing of perl then will try to warn you about them. If a logical name is causing you trouble but is in an LNM table that you do not have write access to then try defining your own to a harmless equivalence string in a table such that it is resolved before the other (e.g. if TMP is defined in the SYSTEM table then try DEFINE TMP "NL:" or somesuch in your process table) otherwise simply deassign the dangerous logical names. The potentially troublesome logicals and symbols are:

    EXT     "LOGICAL"
    FOO     "LOGICAL"
    LIB     "LOGICAL"
    SYS     "LOGICAL"
    T       "LOGICAL"
    TMP     "LOGICAL"
    TEST    "SYMBOL"

As a handy shortcut, the command:

    @ Configure "-des"

(note the quotation marks and case) will choose reasonable defaults automatically (it takes DEC C over Gnu C, DEC C sockets over SOCKETSHR sockets, and either over no sockets). Some options can be given explicitly on the command line; the following example specifies a non-default location for where Perl will be installed:

    @ Configure "-d" "-Dprefix=dka100:[utils.perl5.]"

Note that the installation location would be by default where you unpacked the source with a "_ROOT." appended. For example if you unpacked the perl source into:


Then the PERL_SETUP.COM that gets written out by CONFIGURE.COM will try to DEFINE your installation PERL_ROOT to be:


More help with is available from:

    @ Configure "-h"

See the "Changing compile-time options (optional)" section below to learn even more details about how to influence the outcome of the important configuration step. If you find yourself reconfiguring and rebuilding then be sure to also follow the advice in the "Cleaning up and starting fresh (optional)" and the checklist of items in the "CAVEATS" sections below.

Changing compile-time options (optional) for Perl on VMS

Most of the user definable features of Perl are enabled or disabled in, which processes the hints file config_h.SH. There is code in there to Do The Right Thing, but that may end up being the wrong thing for you. Make sure you understand what you are doing since inappropriate changes to or config_h.SH can render perl unbuildable; odds are that there's nothing in there you'll need to change.

The one exception is the various *DIR install locations. Changing those requires changes in as well. Be really careful if you need to change these, as they can cause some fairly subtle problems.

Socket Support (optional) for Perl on VMS

Perl includes a number of functions for IP sockets, 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. How well integrated they are into the system depends on the stack, your version of VMS, and the version of your C compiler.

The most portable solution uses the SOCKETSHR library. In combination with either UCX or NetLib, this supports all the major TCP stacks (Multinet, Pathways, TCPWare, UCX, and CMU) on all versions of VMS Perl runs on, with all the compilers on both VAX and Alpha. The socket interface is also consistent across versions of VMS and C compilers. It has a problem with UDP sockets when used with Multinet, though, so you should be aware of that.

The other solution available is to use the socket routines built into DEC C. Which routines are available depend on the version of VMS you're running, and require proper UCX emulation by your TCP/IP vendor. Relatively current versions of Multinet, TCPWare, Pathway, and UCX all provide the required libraries--check your manuals or release notes to see if your version is new enough.

Building Perl ^

The configuration script will print out, at the very end, the MMS or MMK command you need to compile perl. Issue it (exactly as printed) to start the build.

Once you issue your MMS or MMK command, sit back and wait. Perl should compile and link without a problem. If a problem does occur check the "CAVEATS" section of this document. If that does not help send some mail to the VMSPERL mailing list. Instructions are in the "Mailing Lists" section of this document.

Testing Perl ^

Once Perl has built cleanly you need to test it to make sure things work. This step is very important since there are always things that can go wrong somehow and yield a dysfunctional Perl for you.

Testing is very easy, though, as there's a full test suite in the perl distribution. To run the tests, enter the *exact* MMS line you used to compile Perl and add the word "test" to the end, like this:

If the compile command was:


then the test command ought to be:

    MMS test

MMS (or MMK) will run all the tests. This may take some time, as there are a lot of tests. If any tests fail, there will be a note made on-screen. At the end of all the tests, a summary of the tests, the number passed and failed, and the time taken will be displayed.

The test driver invoked via MMS TEST has a DCL wrapper ([.VMS]TEST.COM) that downgrades privileges to NETMBX, TMPMBX for the duration of the test run, and then restores them to their prior state upon completion of testing. This is done to ensure that the tests run in a private sandbox and can do no harm to your system even in the unlikely event something goes badly wrong in one of the test scripts while running the tests from a privileged account. A side effect of this safety precaution is that the account used to run the test suite must be the owner of the directory tree in which Perl has been built; otherwise the manipulations of temporary files and directories attempted by some of the tests will fail.

If any tests fail, it means something is wrong with Perl. If the test suite hangs (some tests can take upwards of two or three minutes, or more if you're on an especially slow machine, depending on your machine speed, so don't be hasty), then the test *after* the last one displayed failed. Don't install Perl unless you're confident that you're OK. Regardless of how confident you are, make a bug report to the VMSPerl mailing list.

If one or more tests fail, you can get more information on the failure by issuing this command sequence:

    @ [.VMS]TEST .typ "" "-v" [.subdir]test.T

where ".typ" is the file type of the Perl images you just built (if you didn't do anything special, use .EXE), and "[.subdir]test.T" is the test that failed. For example, with a normal Perl build, if the test indicated that t/op/time failed, then you'd do this:

    @ [.VMS]TEST .EXE "" "-v" [.OP]TIME.T

Note that test names are reported in UNIX syntax and relative to the top-level build directory. When supplying them individually to the test driver, you can use either UNIX or VMS syntax, but you must give the path relative to the [.T] directory and you must also add the .T extension to the filename. So, for example if the test lib/Math/Trig fails, you would run:

    @ [.VMS]TEST .EXE "" -"v" [-.lib.math]trig.t

When you send in a bug report for failed tests, please include the output from this command, which is run from the main source directory:


Note that -"V" really is a capital V in double quotes. This will dump out a couple of screens worth of configuration information, and can help us diagnose the problem. If (and only if) that did not work then try enclosing the output of:

    MMS printconfig

If (and only if) that did not work then try enclosing the output of:

    @ [.vms]myconfig

You may also be asked to provide your C compiler version ("CC/VERSION NL:" with DEC C, "gcc --version" with GNU CC). To obtain the version of MMS or MMK you are running try "MMS/ident" or "MMK /ident". The GNU make version can be identified with "make --version".

Cleaning up and starting fresh (optional) installing Perl on VMS

If you need to recompile from scratch, you have to make sure you clean up first. There is a procedure to do it--enter the *exact* MMS line you used to compile and add "realclean" at the end, like this:

if the compile command was:


then the cleanup command ought to be:

    MMS realclean

If you do not do this things may behave erratically during the subsequent rebuild attempt. They might not, too, so it is best to be sure and do it.

Installing Perl ^

There are several steps you need to take to get Perl installed and running.

  1. Check your default file protections with

    and adjust if necessary with SET PROTECTION=(code)/DEFAULT.

  2. Decide where you want Perl to be installed (unless you have already done so by using the "prefix" configuration parameter -- see the example in the "Configuring the Perl build" section).

    The DCL script PERL_SETUP.COM that is written by CONFIGURE.COM will help you with the definition of the PERL_ROOT and PERLSHR logical names and the PERL foreign command symbol. Take a look at PERL_SETUP.COM and modify it if you want to. The installation process will execute PERL_SETUP.COM and copy files to the directory tree pointed to by the PERL_ROOT logical name defined there, so make sure that you have write access to the parent directory of what will become the root of your Perl installation.

  3. Run the install script via:
        MMS install


        MMK install

    If for some reason it complains about target INSTALL being up to date, throw a /FORCE switch on the MMS or MMK command.

Copy PERL_SETUP.COM to a place accessible to your perl users.

For example:


If you want to have everyone on the system have access to perl then add a line that reads

    $ @sys$library:perl_setup


Two alternatives to the foreign symbol would be to install PERL into DCLTABLES.EXE (Check out the section "Installing Perl into DCLTABLES (optional)" for more information), or put the image in a directory that's in your DCL$PATH (if you're using VMS V6.2 or higher).

An alternative to having PERL_SETUP.COM define the PERLSHR logical name is to simply copy it into the system shareable library directory with:

    copy perl_root:[000000]perlshr.exe sys$share:

See also the "INSTALLing images (optional)" section.

Installing Perl into DCLTABLES (optional) on VMS

Execute the following command file to define PERL as a DCL command. You'll need CMKRNL privilege to install the new dcltables.exe.

    $ create perl.cld
    ! modify to reflect location of your perl.exe
    define verb perl
      image perl_root:[000000]perl.exe
      cliflags (foreign)
    $ set command perl /table=sys$common:[syslib]dcltables.exe -
    $ install replace sys$common:[syslib]dcltables.exe
    $ exit

INSTALLing Perl images (optional) on VMS

On systems that are using perl quite a bit, and particularly those with minimal RAM, you can boost the performance of perl by INSTALLing it as a known image. PERLSHR.EXE is typically larger than 3000 blocks and that is a reasonably large amount of IO to load each time perl is invoked.


should be enough for PERLSHR.EXE (/share implies /header and /open), while /HEADER should do for PERL.EXE (perl.exe is not a shared image).

If your code 'use's modules, check to see if there is a shareable image for them, too. In the base perl build, POSIX, IO, Fcntl, Opcode, SDBM_File, DCLsym, and Stdio, and other extensions all have shared images that can be installed /SHARE.

How much of a win depends on your memory situation, but if you are firing off perl with any regularity (like more than once every 20 seconds or so) it is probably beneficial to INSTALL at least portions of perl.

While there is code in perl to remove privileges as it runs you are advised to NOT INSTALL PERL.EXE with PRIVs!

Running h2ph to create perl header files (optional) on VMS

If using DEC C or Compaq C ensure that you have extracted loose versions of your compiler's header or *.H files. Be sure to check the contents of:



If using GNU cc then also check your GNU_CC:[000000...] tree for the locations of the GNU cc headers.

Reporting Bugs ^

If you come across what you think might be a bug in Perl, please report it. There's a script in PERL_ROOT:[UTILS], perlbug, that walks you through the process of creating a bug report. This script includes details of your installation, and is very handy. Completed bug reports should go to


Probably the single biggest gotcha in compiling Perl is giving the wrong switches to MMS/MMK when you build. Use *exactly* what the script prints!

The next big gotcha is directory depth. Perl can create directories four, five, or even six levels deep during the build, so you don't have to be too deep to start to hit the RMS 8 level limit (for ODS 2 volumes which were common on versions of VMS prior to V7.2 and even with V7.2 on the VAX). It is best to do:

    DEFINE/TRANS=(CONC,TERM) PERLSRC "disk:[dir.dir.dir.perldir.]"

before building in cases where you have to unpack the distribution so deep (note the trailing period in the definition of PERLSRC). Perl modules from CPAN can be just as bad (or worse), so watch out for them, too. Perl's configuration script will warn if it thinks you are too deep (at least on a VAX or on Alpha versions of VMS prior to 7.2). But MakeMaker will not warn you if you start out building a module too deep in a directory.

Be sure that the process that you use to build perl has a PGFLQ greater than 100000. Be sure to have a correct local time zone to UTC offset defined (in seconds) in the logical name SYS$TIMEZONE_DIFFERENTIAL before running the regression test suite. The SYS$MANAGER:UTC$CONFIGURE_TDF.COM procedure will help you set that logical for your system but may require system privileges. For example, a location 5 hours west of UTC (such as the US East coast while not on daylight savings time) would have:


A final thing that causes trouble is leftover pieces from a failed build. If things go wrong make sure you do a "(MMK|MMS|make) realclean" before you rebuild.

DEC C issues with Perl on VMS

Note to DEC C users: Some early versions (pre-5.2, some pre-4. If you're DEC C 5.x or higher, with current patches if any, you're fine) of the DECCRTL contained a few bugs which affect Perl performance:

- pipes

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 DEC C.

- modf()

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 DEC C.


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 ALPACRT04_061 or later. See also:

Please note that in later versions "DEC C" may also be known as "Compaq C".

GNU issues with Perl on VMS

It has been a while since the GNU utilities such as GCC or GNU make were used to build perl on VMS. Hence they may require a great deal of source code modification to work again.

Floating Point Considerations

Prior to 5.8.0, Perl simply accepted the default floating point options of the C compiler, namely representing doubles with D_FLOAT on VAX and G_FLOAT on Alpha. Single precision floating point values are represented in F_FLOAT format when either D_FLOAT or G_FLOAT is in use for doubles. Beginning with 5.8.0, Alpha builds now use IEEE floating point formats by default, which in VMS parlance are S_FLOAT for singles and T_FLOAT for doubles. IEEE is not available on VAX, so F_FLOAT and D_FLOAT remain the defaults for singles and doubles respectively. The available non-default options are G_FLOAT on VAX and D_FLOAT or G_FLOAT on Alpha.

The use of IEEE on Alpha introduces NaN, infinity, and denormalization capabilities not available with D_FLOAT and G_FLOAT. When using one of those non-IEEE formats, silent underflow and overflow are emulated in the conversion of strings to numbers, but it is preferable to get the real thing by using IEEE where possible.

Regardless of what floating point format you consider preferable, be aware that the choice may have an impact on compatibility with external libraries, such as database interfaces, and with existing data, such as data created with the pack function and written to disk, or data stored via the Storable extension. For example, a pack("d", $foo)") will create a D_FLOAT, G_FLOAT, or T_FLOAT depending on what your Perl was configured with. When written to disk, the value can only be retrieved later by a Perl configured with the same floating point option that was in effect when it was created.

To obtain a non-IEEE build on Alpha, simply answer no to the "Use IEEE math?" question during the configuration. To obtain an option different from the C compiler default on either VAX or Alpha, put in the option that you want in answer to the "Any additional cc flags?" question. For example, to obtain a G_FLOAT build on VAX, put in /FLOAT=G_FLOAT.

Multinet issues with Perl on VMS

Prior to the release of Perl 5.8.0 it was noted that the regression test for lib/Net/hostent (in file [.lib.Net]hostent.t) will fail owing to problems with the hostent structure returned by C calls to either gethostbyname() or gethostbyaddr() using DEC or Compaq C with a Multinet TCP/IP stack. The problem was noted in Multinet 4.3A using either Compaq C 6.5 or DEC C 6.0, and with Multinet 4.2A using DEC C 5.2, but could easily affect other versions of Multinet. Process Software Inc. has acknowledged a bug in the Multinet version of UCX$IPC_SHR and has provided an ECO for it. The ECO is called UCX_LIBRARY_EMULATION-010_A044 and is available from:

As of this writing, the ECO is only available for Multinet versions 4.3A and later. You may determine the version of Multinet that you are running using the command:

    multinet show /version

from the DCL command prompt.

If the ECO is unavailable for your version of Multinet and you are unable to upgrade, you might try using Perl programming constructs such as:

    $address = substr($gethostbyname_addr,0,4);

to temporarily work around the problem, or if you are brave and do not mind the possibility of breaking IPv6 addresses, you might modify the pp_sys.c file to add an ad-hoc correction like so:

    --- pp_sys.c;1        Thu May 30 14:42:17 2002
    +++ pp_sys.c        Thu May 30 12:54:02 2002
    @@ -4684,6 +4684,10 @@

    +    if (hent) {
    +        hent->h_length = 4;
    +    }
         if (GIMME != G_ARRAY) {
             PUSHs(sv = sv_newmortal());
             if (hent) {

then re-compile and re-test your perl. After the installation of the Multinet ECO you ought to back out any such changes though.

Mailing Lists ^

There are several mailing lists available to the Perl porter. For VMS specific issues (including both Perl questions and installation problems) there is the VMSPERL mailing list. It is usually a low-volume (10-12 messages a week) mailing list.

To subscribe, send a mail message to VMSPERL-SUBSCRIBE@PERL.ORG. The VMSPERL mailing list address is VMSPERL@PERL.ORG. Any mail sent there gets echoed to all subscribers of the list. There is a searchable archive of the list on the web at:

To unsubscribe from VMSPERL send a message to VMSPERL-UNSUBSCRIBE@PERL.ORG. Be sure to do so from the subscribed account that you are canceling.

Web sites for Perl on VMS

Vmsperl pages on the web include:


Perl information for users and programmers about the port of perl to VMS is available from the [.VMS]PERLVMS.POD file that gets installed as perlvms. For administrators the perlvms document also includes a detailed discussion of extending vmsperl with CPAN modules after Perl has been installed.


Revised 10-October-2001 by Craig Berry Revised 25-February-2000 by Peter Prymmer Revised 27-October-1999 by Craig Berry Revised 01-March-1999 by Dan Sugalski Originally by Charles Bailey


A real big thanks needs to go to Charles Bailey, who is ultimately responsible for Perl 5.004 running on VMS. Without him, nothing the rest of us have done would be at all important.

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
  Peter Prymmer 
     for extensive testing, as well as development work on
     configuration and documentation for VMS Perl,
  Dan Sugalski
     for extensive contributions to recent version support,
     development of VMS-specific extensions, and dissemination
     of information about VMS Perl,
  the Stanford Synchrotron Radiation Laboratory and the
     Laboratory of Nuclear Studies at Cornell University for
     the opportunity to test and develop for the AXP,
  John Hasstedt
     for VAX VMS V7.2 support

and to the entire VMSperl group for useful advice and suggestions. In addition the perl5-porters 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.

Thanks, The VMSperl group

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