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intro to Perl on Windows
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Although Perl may have been born and raised in the
Unix universe, the world's favorite practical extraction
and reporting language has had, and has had for some time,
an established home on Windows.
Led by such companies as ActiveState, Perl has grown steadily
since mid 1995, adding both standard Perl functionality, as
well as a host of Windows-specific functionality such as OLE
and COM integration.
In fact, by now, any Perl developer can feel confident that the
applications she writes on UNIX-based servers will run without
hitch when moved to Windows-based servers. Even long-time porting
nightmare problem cases such as the implementation of fork
are being solved.
And there is reason to believe that Perl/Windows-integration will
continue. That Microsoft itself is committed to supporting Perl
is demonstrated by the fact that Microsoft has been a major funder
of Perl on Windows development since development began. In fact,
with the recent signing of a three-year funding agreement between
Microsoft and ActiveState, there is no doubt Perl will be an integral
part of Windows going forward.
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Whether you are simply wishing to begin an investigation of the
core language and your platform happens be Windows or whether you
wish to look at specific-Windows integration tools such as 1) OLE
[ object linking and Embedding ] with PERL, 2) control of the Windows
registry via PERL, 3) using PERL to write COM [ Component Object
Model ] objects, 4) communicating with pre existing COM objects
from PERL, or 5) facilitating data aware pages via the PERLscript
and IIS [ Internet Information Server ], your starting point remains
the same - the installation of PERL on Windows.
This article is intended as a guide to that process. Future additions
will delve more deeply into the Windows-specific capabilities of Perl.
Before you start though, we have one warning. Installing Perl is not
a "click here and you're done" process. In fact, packaging Perl for
Windows is an iterative process. Because Perl is an incredibly active,
vibrant and living language, not only does the core language itself
undergo changes and new releases periodically, but the thousands of
your fellow Perl developers constantly release new, free tools through
archives such as CPAN. Thus, "installation" includes regular upgrades
and your active attention to the world of Perl.
As we mentioned earlier, the organisation at the heart of Perl for
Windows is ActiveState, and their home page is located at:
http://www.activestate.com
Perl for Windows is available from the ActiveState site as a product
called ActivePerl. At the time of this writing, ActivePerl is in
release 522 and can be downloaded directly from
http://www.activestate.com/ActivePerl/download.htm.
Windows users will want to download the Intel release, and
as the download page notes, those who are installing the package
under Windows 95 require DCOM for Windows, Available from the
Microsoft Site. Whether you download the package using HTTP or
FTP does not really matter. Either way, you'll get what you are
after.
When you are done downloading, you'll have a self-extracting
executable such as the file Api509e.exe shown in the figure
below. To begin the installation process, just double click
the file.
It is important to note that the installation of ActivePerl may
not proceed correctly if your system has a previously installed
version AND that version is in use by a process at the time you
commence your installation. If that is the case, you may be
presented with a warning dialog box.
If this happens, you should exit the installation process
immediately. Close any services/applications that may be
using Perl and try again.
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If you are having trouble locating Perl-based services and you
happen to be using Windows NT, you can get help by using:
Start->Settings->Control Panel->Services
Look through the
list of services running on your machine to see if you can
find one that may currently be using Perl. Terminate it/them,
and then recommence your installation.
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Most users of course will not have to worry about this problem.
In fact, most likely, if you double clicked the self-extracting
executable, you will now see the ActiveState license agreement.
After you have read and accepted the license, you will be presented
with the "Installation Notes" screen. This screen informs you of
all the different installation options that are available with
ActivePerl. This page has a number of different headings, and
some explanation regarding each.
The headings include:
 Add the Perl bin directory to your path
Associate '.pl' with Perl.exe in Explorer
Associate '.pl' with Perl.exe for your Web server(s)
Associate '.plx' with Perl for ISAPI in IIS
It then asks if you have read and understand the notes. Let's
make sure that you do!
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Add the Perl bin directory to your path
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Oftentimes, it is convenient to be able to run the Perl
executable from within a DOS session without having to
explicitly specify in which directory Perl is installed.
For example, suppose you just want to be able to type:
perl scriptname.plx
from the command line rather than having to type:
c:\perl\bin\perl.exe scriptname.plx
In order to do that, you need to let your computer know where
perl.exe is located. And in order to do that, you need to
modify the PATH environment variable. In this section, Perl
is letting you know that it is going to automatically modify
the PATH variable on your behalf.
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Note that by including the Perl "bin" directory in your path
also means that your computer will automatically know where
other related programs are as well such as perldoc.
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However, you should note the significance of the statement
"...all other Perl directories to be removed from the PATH.".
Bear in mind that after this installation, you will have to
add to the path the location of any different installations
of Perl that you may wish to use concurrently. However, most
users will be satisfied with a single installation and will
not need to worry about this.
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Associate '.pl' with Perl.exe in Explorer
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This note is relatively self-explanatory. This option means
that every time you double click on a file suffixed ".pl" in
Windows explorer, your machine will use the Perl interpreter
to execute the file. The behaviour you will see is that a
"Command Prompt" window will appear, and the Perl script will
be executed within it.
The practical effect of this can be seen after you have completed
your installation of Perl.
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Associate '.pl' with Perl.exe for your Web server(s)
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Associating the .pl extension with the Perl interpreter in Windows
Explorer is convenient for you as a developer because you can more
easily run scripts. However, if you are a web developer, you also
need to associate the extension from the point of view of the web
severs you are using. That way, the web server will have a better
idea of what a Perl script is.
On a systems level, associating the extension with Perl.exe for
your web server means that the installer will edit your windows
registry that will instruct IIS to associate scripts with a ".pl"
extension as being suitable for execution by the Perl interpreter.
More importantly, the standard error and standard output generated
by Perl scripts will be printed directly to the browser. This is
a core feature from the point of view of writing CGI [ Common
Gateway Interface ] scripts.
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Associate '.plx' with Perl for ISAPI in IIS
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The effect of this installation option is that the execution of
Perl scripts through the web server will be optimised. ISAPI
stands for Internet Server Application Programming Interface.
The way that the execution of Perl scripts by the web server
usually works is that as a preliminary step to the execution
of the script, the web server has to actually load the Perl
interpreter into memory. It does this every time the CGI is called.
The use of ISAPI means that the web server has access to the
Perl interpreter bundled as a runtime DLL that can be loaded
once by the web server. Once loaded the interpret will persist
in memory and not need to be reloaded for subsequent CGI calls.
This functionality is only available if you have installed a web
server that implements the ISAPI.
There are security/stability implications associated with running
Perl in the same thread of execution as the web server [as opposed
to starting a separate process to load the Perl interpreter and
execute the CGI ]. However, aside from mentioning them, these
matters are outside the scope of this article.
An associated point is that loading the Perl interpreter as a
persistent DLL in the web server makes it even more important
to close down IIS prior to installing a new version of ActivePerl.
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Choosing an Installation Directory
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Answering "yes" to the "Installation Notes" screen will advance
you to the "Choose Destination Location" Screen.
This screen allows you to select a root directory for the
installation of Perl. The choice is entirely yours, but the
default path is to be recommended from the point of view of
installing subsequent versions of ActivePerl over the top of
old versions.
One thing to note is that if you wish to regularly move Perl
scripts between UNIX and Windows servers, it might be a good
idea to create a "c:\usr\bin" directory and copy the contents
of the c:\Perl\bin" directory into it. That way, you can use
the same Perl header line in all your Perl scripts.
#!/usr/bin/perl
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Once you have specified the installation path, you will be
asked to choose which ActivePerl components you would like
installed.
Most of these options have been explained above.
However, we have not yet talked about
PerlScript.
The PerlScript component
gives you the ability to write web pages that contain embedded
Perl code that the web server will be able to execute.
In other words, you will be able to write ASP pages in PERL.
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The next screen will query you regarding the addition of Perl bin
to your path and the association of .pl files with Perl.exe in
Windows Explorer and the web server.
We have already covered these topics above. Just notice that you can
uncheck any of the boxes that you are not comfortable with.
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Adding Perl to the Start Menu
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Next, the ActivePerl installer will create an icon on your Start menubar for
its associated functions. This screen helps you select where you want
this icon to be created.
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Finally, the installer will provide a summary screen as a final check
and ask you if it is okay to begin the installation process.
Clicking next will begin the installation process. Just wait while the
installer does its work.
After the installation is complete, and you have/have not read
the release notes, start a command prompt (DOS Shell) window. If typing
"perl -v" prints out a message containing version information
about your installation of Perl, then the installation process
is successfully complete.
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If you are a new Perl developer, you can get an excellent
introduction to standard cross-platform Perl programming at
The
Introduction to Web Programming Tutorial and at
The
Introduction to Perl 5 Tutorial.
Otherwise, here is a quick demonstration of a very simple perl program
written using Notepad and run from the DOS Shell.
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