Perl is a high-level programming language with an eclectic heritage written by Larry Wall. Perl like Javascript is a scripting language which adds interactivity to web site pages. You can find bulletin boards, chat rooms and a wide variety of other web site applications that are written in Perl. Perl derives from the ubiquitous C programming language and to a lesser extent from sed, awk, the Unix shell, and at least a dozen other tools and languages. Perl is great for creating programs for web sites such as,
- system utilities,
- software tools,
- system management tasks,
- database access,
- graphical programming,
- networking, and
- world wide web programming.
Perl builds and runs on a number of platforms,
- Virtually all known and current Unix derivatives are supported (Perl's native platform)
- VMS,
- DOS,
- OS/2,
- Windows,
- QNX,
- BeOS,
- Amiga
Perl FAQ
- How can I compile Perl
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To compile Perl you need a C compiler on your machine. If your vendor did not include one with your system, then grab a binary version of gcc from the net,
check,
If you are on a UNIX its probably best to compile Perl yourself from the source code distribution. If you are on Windows or MacOS, you will probably be best with a binary build.
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- Perl scripting basics
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If you are looking to understand a perl script, then these are common elements you may find,
- # - comment and this line wont get executed.
- $ - indicates that this is a variable
- & - if a word starts with a & it is a call to a sub-routine
- < - the file is being opened for a read operation
- > - the file is being opened for a write operation
- >> - the file is being opened for an append operation
- (.) - this puts together two variables
- @ - if a word start with this character it indicates a single-dimension array
- % - if a word starting with this character indicates a two-dimensional array.
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- Perl versions
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Version 4
- was the fourth major release (March 1991)
- it's stable but,
- is old, limited, and no longer maintained;
- its last patch (4.036) was in 1992
Version 5
- name for the fifth major release (October 1994)
- rewrite of the original perl source code from releases 1 through 4
- has been modularized, object-oriented, tweaked, trimmed, and optimized
- interface is mostly the same
Version 6
- rewrite of the current release of Perl by the Topaz project
- 100% source-compatibility with previous releases
- written in nominally portable C++
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- Reporting Perl bugs
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If you are reporting a bug in the perl interpreter or the modules shipped with Perl, email Perl at this address,
- perlbug@perl.com
If you are posting a bug with a non-standard port, a binary distribution, or a non-standard module then you will need to check the documentation that came with it to determine the correct place to post bugs.
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- How to start a cgi script with Perl interpreter
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Most web servers require this line at the start of any cgi script that uses a perl interpreter,
- #!/usr/local/bin/perl (often the Perl 5 location) , or this,
- #!/usr/bin/perl (often the Perl 4 location)
If this causes an error then asked your web host for it's perl compiler path details.
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- Basic Perl Script
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To test your ability to store and run a Perl program, enter and execute something like this,
#!/usr/local/bin/perl -w
if ($#ARGV >= 0) { $who = join(' ', @ARGV); }
else { $who = 'World'; }
print "Hello, $who!\n";this should print "Hello" on your screen.
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- How to make your Perl CGI script more efficient
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Each time a GCI script runs it will need to be re-compiled by Perl and will often allocate a megabyte or more of system memory, this can be a killer.
There are two popular ways to avoid this overhead.
- One is running the Apache HTTP server with either of the mod_perl or mod_fastcgi plugin modules.
- Two running it with the FCGI module (from CPAN) and the mod_fastcgi module (available from http://www.fastcgi.com/) each of your Perl programs becomes a permanent CGI daemon process.
These solutions can both effect your system and how you write your CGI programs, so investigate how them carefully.
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