Running Perl

There are a lot of ways of running Perl, it depends on what you intend to do and the platform on which Perl is installed. Before playing with Perl, you must check if you have a proper Perl version installed. For this, you may run the following command from a command prompt:

perl –v

which will tell you if Perl is installed and if so, what version it is.

Now let’s see a few ways of running Perl and what possibilities we have in view.

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1. The simplest way for running Perl is from a command line as in the following example:

>perl -e "print qq[Hello world!\n]"

This simple command will print on the screen the classic welcome message "Hello world!". As you see in our example, the entire program code was included between double quotes. We can do this only with very small programs which we can include into a command line. It is very useful if we want to verify how a short sample of Perl code works.

2. Another way for running Perl is to use for the program line of code the standard input stream like in the example below:

>perl
print "Hello World!\n";
$pi=3.14159;
print $pi;
^Z

Note that the last character of the program is Ctrl/Z, which is the indicator for the End of File. This example has the inconvenience that your program code is saved only temporally and will be lost after the execution. You can use this method if you want to verify some code samples or play a bit with Perl. 3. If you want to do some serious work with Perl, you must use an editor (such as Emacs for Linux and UltraEdit for Windows – but you can check our link Perl Editors too) to edit and save your Perl code in a file. Don’t forget to use the .pl extension for your Perl file.

The file Hello.pl shown below is a very simple example of a Perl script:

Hello.pl
#!/usr/bin/perl
print "Hello World";

The program has only 2 lines, the first one tells where Perl is located and the second one prints the message "Hello World". We will run this program from a command prompt window.

In Linux we must first make our program executable:

>chmod u+x Hello.pl

and the next step is to run the program:

>Hello.pl

>perl Hello.pl

In Windows running Perl script means typing in the following command in a command prompt window:

>perl Hello.pl

If you want to see the warnings of the program, you can use the command:

>perl –w Hello.pl

or the command:

>perl –d Hello.pl

if you want to run Perl with the debugger support.

4. After verifying your program on your local computer and everything looks ok and if this program is written for a web site, you must upload your Perl file on the web site and then run it from your browser. We’ll show you how to do this by looking at the following Perl file example:

Hello.pl

#!/usr/bin/perl
print "Content-Type: text/html \n\n";
print "Hello World";

The program included in the above file has only 3 lines;

the first line tells the Web server where Perl is located, that is /usr/bin/perl
the second line tells the Web browser that will follow some text or HTML code
the third line is a print command and it will print the words "Hello World" in the window browser

The next steps include the uploading (generally through a FTP client) of your script on your web server in the cgi-bin directory and the setting up of the script permissions. After that, you can create a simple web page to run the script, by creating the file Hello.html:

and running it from your favorite browser.

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Table of Contents:

A Perl Script
Install Perl
Running Perl (more)
Perl Data Types
Perl Variables
Perl Operators
Perl Lists
Perl Arrays
    Array Size
    Array Length
Perl Hashes
Perl Statements
    Perl if
    Perl unless
    Perl switch
    Perl while
    Perl do-while
    Perl until
    Perl do-until
    Perl for
    Perl foreach
Built-in Perl Functions
    Functions by Category
        String Functions
        Regular Expressions and Pattern Matching
        List Functions
        Array Functions
        Hash Functions
        Miscellaneous Functions
    Functions in alphabetical order
        chomp
        chop
        chr
        crypt
        defined
        delete
        each
        exists
        grep
        hex
        index
        join
        keys
        lc
        lcfirst
        length
        map
        oct
        ord
        pack
        pop
        push
        q
        qq
        qw
        reverse
        rindex
        scalar
        shift
        sort
        splice
        split
        sprintf
        substr
        tr
        uc
        ucfirst
        undef
        unpack
        unshift
        values

return from Running Perl to Perl Basics

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