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Roger J. Wendell
Defending 3.8 Billion Years of Organic Evolution^SM

Perl: Practical Extraction and Reporting Language Perl is a general-purpose programming language that was developed by Larry Wall. First released in 1987, Perl was originally developed for text manipulation but is now used for wide range of tasks. Perl has become a popular language for writing CGI scripts and is easy to use for building and testing simple programs...

Click Here for my main computer page...

Click Here for my UNIX page...

Y = CX^2 + B pico parabola.pl perl parabola.pl -2 3 cat parabola.data gnuplot plot "parabola.data" quit

#!/usr/bin/perl # experimenting with a parabola 12-25-2007 # c is the concavity of the parabola # Y = CX^2 + B # B is the intercept with the Y axis # ARGV is argument variable containing the arguments # to the program on the command line   $c = $ARGV[0]; $b = $ARGV[1]; open (filehandle, ">parabola.data"); for ( $x = -10; $x<=10; $x=$x+.1 )   {        $y = $c * $x * $x + $b;        print filehandle $x, " ", $y, "\n";   }   close (filehandle);

Under UNIX, Perl acts like a shell interpreter.
Most UNIX systems store Perl in /usr/bin/perl

• perl -v (What version of Perl are you running?)
• whereis perl (Where the heck is Perl on my machine?)
           /usr/bin/perl
           /usr/contrib/bin/perl (a typical answer)

In Perl, numbers and strings are the basic unit of conversation and are called scalars. Scalars that represent information that does not change over the life of the program are called constants or literals. Examples of literals are pi (3.14159265...), the name of the fourth planet from the sun (Mars), or the absolute limit of causal interation (299,792,458 metres per second [1,079,252,849 km/h]).

In Perl, scalars that change are called scalar variables. You can change the contents of a variable because they merely act as as handles for the data they represent. Variable are usually given convenient and easy-to-remember names that allow you to easily refer to the data you are manipulating.

Perl Operators

• x          Character repeat and list repeat
• .          Sting concatenation
• =          Assignment
• +          Add
• -          Subtract
• *          Multiply
• /          Divide
• %          Modulo Divide
• -          Unary negation: negates the number that it precedes
• +          Unary plus does nothing but return the operand in its original form, thereby having no effect on the operand
• *          Raise to the power
• ++          Unary increment: can be used before or after a variable to increment before or after the variable is evaluated.
• _          Unary decrement: can be used before or after a variable to decrement before or after the variable is evaluated.
• += .=          Assignment after operation.

Simple bits of Code:

  #!/usr/local/bin/perl 
   print "Hello, world!\n"; 

# file: time.pl
  $time = localtime;
  print "The time is now $time\n";

Perl References and Related Stuff:

• ActiveState - Industry-standard Perl distribution
• CPAN - Comprehensive Perl Archive Network
• GNOME Project - Free desktop environment
• GNU Project - Free Unix-like operating system
• PERL - The Source for Perl
• TPJ - The Perl Journal, purportedly and excellent resource, printed its
  last issue in January, 2006. I'd link their site but it no longer exists...

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