In Perl, numbers and strings are called scalars. Scalars that do not change during the lifetime of a program are known as constants or literals. Scalars that do change are known as variables. Operators do something with scalars, for example, add together the contents of two variables.

Literals/Constants

There are two types of literal:

* numeric literals, for example, 6, 8.5, 11, 17.678, and so on, and
* string literals, for example, “hello world”.

Numeric literals may be integers, for example, 6, floating point, for example, 12.5, or scientific notation, for example, 2e10. Strings are a sequence of characters, for example, goodbye cruel world.

Scalar Variables

Data that may change during the lifetime of a program is stored in variables, for example, $total. The dollar ($) sign is called a type identifier, and tells Perl that the variable contains scalar data.

Variable names can contain alphanumeric characters (a-z, A-Z, and 0-9) and the underscore character, and are case-sensitive.

Expressions and Operators

Perl programs are collections of expressions and statements that, by default, are executed in the order in which they appear in the program.

1. #!/usr/bin/perl -w
2. $radius=10;
3. $pi=3.1415927;
4. $area=$pi*($radius**2);
5. print $area;

The equals sign (=) is known as the assignment operator. It takes the value on its right-hand side, and puts it in the variable on the left. The star (*) is the multiplication operator. Two stars together (**) indicate ‘to the power of’.

Another example:

1. $a=”Goodbye”;
2. $b=”cruel world”;
3. $c=$a.$b;
4. print $c;

The dot (.) concatenates the contents of variables $a and $b, and the result is put into variable $c.

Open a text editor, for example, NotePad, and enter the following lines of code:

#!/usr/bin/perl -w

print “Monthly deposit: “; # prompt for input
$deposit=; # get input from keyboard
chomp $deposit; # remove the newline character from the end of the variable

print “Interest rate (3, 4, 5.5, etc): “; # prompt for input
$interest=; # get input from keyboard
chomp $interest; # remove the newline character from the end of the variable

# Change interest from 3, 4, 5, etc to .03, .04, .05, etc
$interest=$interest*.01;

# Change interest to a monthly multiplier
$interest=$interest/12;

print “No of months: “; # prompt for input
$nMonths=; # get input from keyboard
chomp $nMonths; # remove the newline character from the end of the variable

# The interest calculation
$total=$deposit * (((1 + $interest) ** $nMonths) -1 ) / $interest;

print “After $nMonths months you will have a total amount of $total”;

(Note: the spaces on either side of STDIN are for display purposes only in this article. In your script, you can omit them.)

Save the script as interest.pl. Make a note of the directory/folder where you have saved it.

Running the script

You need to run the script from a command line prompt, so open a terminal window/MS-DOS prompt. Change to the directory/folder where the interest.pl file is located, and type the following command:

perl interest.pl

When prompted, enter the monthly deposit, interest rate, and the number of months that the money is deposited.

Error messages

If the script did not work, you probably received one of the following error messages:

* ‘Bad command or filename’ or ‘command not found’. This means that Perl has not been added to the PATH variable. See your operating system help/documentation for information on how to fix this problem.
* ‘Can’t open perl script interest.pl: A file or directory does not exist’. This probably means that you are not in the folder/directory where you saved the script, in which case you should change to the correct location.
* If you get a syntax error, it probably means you have mis-typed the contents of the file. Open the file and fix any mistakes.

Perl programming language is a language which is ideal solution for creating dynamic web pages and also has the ability to perform system management task. Released in 1987, it was designed to provide efficiency and simplicity. There are many benefits in using Perl and this article will elaborate on that.

The first thing that comes to mind is its effectiveness in providing cleaner code. With the new Perl 5, codes are far more readable than before. Cryptic variables can now be replaced by mnemonic identifiers. Error messages that you get is even more informative and understandable. This is a great help for new webmasters and developers.

The library in the Perl 5 is defined in modules. This can be shared between various packages. All users need to do is just import them. It can be done on a single module or the entire module. Furthermore, the same action can be done with pragmas and compiler directives. This programming language is also very object-orientated. It supports dynamic inheritance and virtual methods in a very straightforward way. There is a little need for syntax and the packages can be used as file handlers can be treated as an object.

With the ability to be embedded into C or C++ applications, Perl 5 is high compatibility and extensibility. It has a IX processor that can allow users to easily paste C or C+ routines into a framework. This is supported by dynamic module loading. Therefore, Perl itself can act as a dynamic library. One of its latest modules POSIX provides access to all available POSIX definitions and routine through objects when users need them. Therefore, it is POSIX compliant.

Additional features of Perl are it can simultaneously access DBM, GDBM, NDBM and SDBM from the same script. It has a DBMOpen interface which can allow any variables to connect to an object class that recognizes its access method. It also possesses auto subroutine upload function that allows users to define arbitrary semantics for any routine call which is not defined.

In addition, it also allows users to write regular expressions complete with embedded whitespace for better visual experience. It also has lexical scoping that is similar to auto variables in the C language but more efficient and provides better privacy.

All and all, users will be able to enjoy all this just by downloading it from the free software package at the Perl official website or get a web hosting service that comes with it.

The overall structure of Perl derives broadly from C. Perl is procedural in nature, with variables, expressions, assignment statements, brace-delimited blocks, control structures, and subroutines.

Perl also takes features from shell programming. All variables are marked with leading sigils, which unambiguously identify the data type (for example, scalar, array, hash) of the variable in context. Importantly, sigils allow variables to be interpolated directly into strings. Perl has many built-in functions that provide tools often used in shell programming (although many of these tools are implemented by programs external to the shell) such as sorting, and calling on system facilities.

Perl takes lists from Lisp, hashes (“associative arrays”) from AWK, and regular expressions from sed. These simplify and facilitate many parsing, text-handling, and data-management tasks.

Perl 5 added features that support complex data structures, first-class functions (that is, closures as values), and an object-oriented programming model. These include references, packages, class-based method dispatch, and lexically scoped variables, along with compiler directives (for example, the strict pragma). A major additional feature introduced with Perl 5 was the ability to package code as reusable modules. Larry Wall later stated that “The whole intent of Perl 5’s module system was to encourage the growth of Perl culture rather than the Perl core.”

All versions of Perl do automatic data-typing and automatic memory-management. The interpreter knows the type and storage requirements of every data object in the program; it allocates and frees storage for them as necessary using reference counting (so it cannot deallocate circular data structures without manual intervention). Legal type-conversions — for example, conversions from number to string — are done automatically at run time; illegal type conversions are fatal errors.

With all of the available web hosting plans, now is the time to start building sites whether your goal is fun, education, profit or all of the above. The days of plain static HTML sites is past. Today’s servers feature access to programming languages and database capability to provide dynamic web pages with just a little bit of coding. You may have run across a new word, lampp. Lampp is an acronym for Linux, Apache, Mysql, PHP, and Perl. Keep reading to see why these words are important to you.

L – The Linux operating system, open source, fast and flexible, and constantly being approved
A – The Apache web server, the framework for your website
M – Mysql – the most popular open source database
P – PHP – a flexible scripting language that makes it easy to create dynamic web pages
P – Perl – the old standby language of the web, excellent for text manipulation and data analysis

An excellent example of the use of lampp is the blogging software, WordPress. It is also a case study in the success of the open source community. Beginning with some simple code in 2003, it has evolved into a sophisticated blogging and content management system through the efforts of thousands of volunteer contributors. Today there are hundreds of available plugins (add in features to increase the flexibility, performance, and ease of administration of your blog) and and an almost infinite number of easily loaded themes to change the total look of your site with the click of the mouse.

Software is also available to produce database driven niche sites. It is easy to template sites to display complete catalogs of products with descriptions,available options, images, and just about any thing else you might desire.

All this capability may be overwhelming. It is reassuring to know that you can construct full featured sites offline. Xampp can be downloaded from their site and installed on a windows computer in just a few minutes. With it on your home computer, you can create databases,try out several content management systems, experiment with themes, and see just how easy it is to work with databases. All this without worrying about the search engines finding and displaying the mistakes that go with your early education efforts. If you don’t want to be a geek, that’s OK. Just try some of the open source blogging and content management systems to see how easy and simple it is to build and maintain web sites.

Perl programming language is a language which is ideal solution for creating dynamic web pages and also has the ability to perform system management task. Released in 1987, it was designed to provide efficiency and simplicity. There are many benefits in using Perl and this article will elaborate on that.

The first thing that comes to mind is its effectiveness in providing cleaner code. With the new Perl 5, codes are far more readable than before. Cryptic variables can now be replaced by mnemonic identifiers. Error messages that you get is even more informative and understandable. This is a great help for new webmasters and developers.

The library in the Perl 5 is defined in modules. This can be shared between various packages. All users need to do is just import them. It can be done on a single module or the entire module. Furthermore, the same action can be done with pragmas and compiler directives. This programming language is also very object-orientated. It supports dynamic inheritance and virtual methods in a very straightforward way. There is a little need for syntax and the packages can be used as file handlers can be treated as an object.

With the ability to be embedded into C or C++ applications, Perl 5 is high compatibility and extensibility. It has a IX processor that can allow users to easily paste C or C+ routines into a framework. This is supported by dynamic module loading. Therefore, Perl itself can act as a dynamic library. One of its latest modules POSIX provides access to all available POSIX definitions and routine through objects when users need them. Therefore, it is POSIX compliant.

Additional features of Perl are it can simultaneously access DBM, GDBM, NDBM and SDBM from the same script. It has a DBMOpen interface which can allow any variables to connect to an object class that recognizes its access method. It also possesses auto subroutine upload function that allows users to define arbitrary semantics for any routine call which is not defined.

In addition, it also allows users to write regular expressions complete with embedded whitespace for better visual experience. It also has lexical scoping that is similar to auto variables in the C language but more efficient and provides better privacy.

All and all, users will be able to enjoy all this just by downloading it from the free software package at the Perl official website or get a web hosting service that comes with it.

Like many web content authors, over the past few years I’ve had many occasions when I’ve needed to clean up a bunch of HTML files that have been generated by a word processor or publishing package. Initially, I used to clean up the files manually, opening each one in turn, and making the same set of updates to each one. This works fine when you only have a few files to fix, but when you have hundreds or even thousands to do, you can very quickly be looking at weeks or even months of work. A few years ago someone put me on to the idea of using Perl and regular expressions to perform this ‘cleaning up’ process.

The Goal

When converting documents into HTML the goal is always to achieve a seamless conversion from the source document (for example, a word processor document) to HTML. The last thing you need is for your content authors to be spending hours, or even days, fixing untidy HTML code after it has been converted.

Many applications offer excellent tools for converting documents to HTML and, in combination with a well designed cascading style sheet (CSS), can often produce perfect results. Sometimes though, there are little bits of HTML code that are a bit messy, normally caused by authors not applying paragraph tags or styles correctly in the source document.

Why Perl?

The reason why Perl is such a good language to use for this task is because it is excellent at processing text files, which let’s face it, is all HTML files are. Perl is also the de facto standard for the use of regular expressions, which you can use to search for, and replace/change, bits of text or code in a file.

What is Perl?

Perl (Practical Extraction and Report Language) is a general purpose programming language, which means it can be used to do anything that any other programming language can do. Having said that, Perl is very good at doing certain things, and not so good at others. Although you could do it, you wouldn’t normally develop a user interface in Perl as it would be much easier to use a language like Visual Basic to do this. What Perl is really good at, is processing text. This makes it a great choice for manipulating HTML files.

What is a Regular Expression?

A regular expression is a string that describes or matches a set of strings, according to certain syntax rules. Regular expressions are not unique to Perl – many languages, including JavaScript and PHP can use them – but Perl handles them better than any other language.

To use the Perl programming language you must install a Perl interpreter. Depending on the operating system you are using, it is possible that the interpreter may be already installed. To see whether it is installed, go to a command prompt and enter:

perl -v

If you get a message like ‘command not found’ or ‘Bad command or file name’, it means that the interpreter is not installed or the path of the interpreter has not been added to the system (environment) variable (in Windows).

If it is installed, its version number along with a few other bits of information will be printed (displayed on the screen).

Installing Perl on Windows

ActiveState Tool Corp provides a self-installing Perl distribution. You can download and install this from the ActiveState.com website.

Make sure that the location of the interpreter is added to the path variable (in environment variables), which is accessible via the Control Panel.

Installing Perl on Unix

You can download Perl from the perl.com website. Make sure that you download the ’stable’ or ‘production’ version and not a version that is still being developed and tested.

Installing Perl on a Macintosh

You can download and install Perl for a Macintosh from the perl.com website.

Documentation

With every installation, you get a full copy of the latest version of the documentation. Once the software is installed, you can access the documentation from the command line by entering the following command:

perldoc perl

You may also be able to access an HTML version of the documentation, which you can view in a browser. For a Windows installation, this would typically be found at C:Perlhtmlindex.html.

OptiPerl will help you create CGI & console scripts in Perl, offline in Windows. It is a fully integrated visual developing environment and editor for creating, testing, debugging and running perl scripts, directly or through associated html documents.

Features include:

* Offline editing of Perl scripts in IDE.
* Complete emulation of a real server – scripts can be run indirectly from html documents.
* Live preview of the scripts in the internal web browser.
* Feature packed editor with syntax highlighting.
* Completely integrated debugging with live evaluation of expressions, watches, breakpoints, flow control.
Remote debugging of scripts located on your web server.
* Code completion, and hints while programming.
Automatic syntax checking.
* Box and line coding give a better view of your code.
* Saveable desktops.
* Code librarian that supports ZIP files and code templates.
* Context sensitive help on core perl and module documentation.
* Powerful query editor to create the environment and data sent when calling CGI scripts.
* Many tools like URL Encoder, Perl Printer, Pod Viewer and others.
* Projects to organize and publish a set of scripts.
* Version converter to handle non supported perl functions in windows.
* Opening, saving and running scripts on remote servers.
* Printing script and exporting as HTML with syntax highlighting.
* Searching and replacing with regular expressions in projects and files.
* Extremely versatile user tools. You can create perl code to integrate with the editor. CVS support.
* File and FTP explorer.

Why should you buy this program? Consider the following:

OptiPerl is a great learning tool. You can use it to learn Perl and CGI programming in the comfort of a visual editor, without loss of time and money because of loading from dos perl or being for hours on the internet.

So if you program for hobby or want to introduce yourself in a pleasant way to CGI programming, OptiPerl is for you.

Professionals designing perl programs and cgi scripts use it. You can save much time by quickly creating, debugging and testing all the ideas you have increasing productivity.

For novice or advanced users, for hobby or professional use, OptiPerl is bundled with all the tools you need to make CGI in Perl Programming easy!

Perl 5 isn’t perfect, though, and some of its flaws are more apparent the closer Perl 6 comes to completion.

Perhaps the biggest imperfection of Perl 5 is its internals. Though much of the design is clever, there are also places of

obsolescence and interdependence, as well as optimizations that no one remembers, but no one can delete without affecting too

many other parts of the system. Refactoring an eleven-plus-year-old software project that runs on seventy-odd platforms and

has to retain backwards compatibility with itself on many levels is daunting, and there are few people qualified to do it.

It’s also exceedingly difficult to recruit new people for such a task.

Backwards compatibility in general hampers Perl 5 in other ways. Even though stability of interface and behavior is good in

many ways, baking in an almost-right idea makes it difficult to sell people on the absolutely right idea later, especially if

it takes years to discover what the true solution really is. For example, the long-deprecated and long-denigrated pseudohash

feature was, partly, a way to improve object orientation. However, the Perl 6 approach (using opaque objects) solves the same

problem without introducing the complexity and performance problems that pseudohashes did.

As another example, it’s much too late to remove formats from Perl 5 without breaking backwards compatibility from Perl 1.

However, using formats requires the use of global variables (or scary trickery), with all of the associated maintainability

and encapsulation problems.

This points to one of the most subtle flaws of Perl 5: its single implementation is its specification. Certainly there is a

growing test suite that explores Perl’s behavior in known situations, but too many of these tests exist to ensure that no one

accidentally breaks an obscure feature of a particular implementation that no one really thought about but someone somewhere

relies on in an important piece of code. You could recreate Perl from its tests–after a fashion.