PERL - Define Some Variables

A variable is defined by the ($) symbol (scalar), the (@) symbol (arrays), or the (%) symbol (hashes).
Here is what each type of variable should look like inside of a script.

definevariables.pl:

#!/usr/bin/perl

print "Content-type: text/html \n\n"; #HTTP HEADER

$somenumber = 4;
$myname = "some string";
@array = ("value00","value01","value02");
%hash = ("Quarter", 25, "Dime", 10, "Nickle", 5);
## OR ##
my $somenumber = 4;
my $myname = "some string";
my @array = ("value00", "value01", "value02");
my %hash = ("Quarter", 25, "Dime", 10, "Nickle", 5);

The latter example using the my parameter is another means to define a variable that you might run across as you gain more experience. It is not necessary to use the my parameter. Variables can be defined either way.

Perl - Scalar Variables

Scalar variables are simple variables containing only one element--a string, a number, or a reference. Strings may contain any symbol, letter, or number. Numbers may contain exponents, integers, or decimal values. The bottom line here with scalar variables is that they contain only one single piece of data. What you see is what you get with scalar variables.

definescalars.pl:

#!/usr/bin/perl

print "Content-type: text/html \n\n"; #HTTP HEADER

# DEFINE SOME SCALAR VARIABLES
$number = 5;
$exponent = "2 ** 8";
$string = "Hello, Perl!";
$stringpart_1 = "Hello, ";
$stringpart_2 = "Perl!";
$linebreak = "<br />"; #HTML LINEBREAK TAG

# PRINT THEM TO THE BROWSER
print $number;
print $linebreak;
print $exponent;
print $linebreak;
print $string.$linebreak;
print $stringpart_1.$stringpart_2;

Display:

5
2 ** 8
Hello, Perl!
Hello, Perl!

Scalars are very straight forward. Notice that we used a period (.) between each of our variables. This is a special kind of operator that concatenates two or more variables.

Perl - Array Variables

Arrays contain a list of scalar data (single elements). A list can hold an unlimited number of elements. In Perl, arrays are defined with the at (@) symbol.

definearrays.pl:

#!/usr/bin/perl

print "Content-type: text/html \n\n"; #HTTP HEADER

#DEFINE SOME ARRAYS
@days = ("Monday", "Tuesday", "Wednesday");
@months = ("April", "May", "June");

#PRINT MY ARRAYS TO THE BROWSER
print @days;
print "<br />";
print @months;

Display:

MondayTuesdayWednesday
AprilMayJune

Perl - Define A Hash

Hashes are complex lists with both a key and a value part for each element of the list. We define a hash using the percent symbol (%).

definehashes.pl:

print "Content-type: text/html \n\n"; #HTTP HEADER

#DEFINE SOME ARRAYS
%coins = ("Quarter", 25, "Dime", 10, "Nickle", 5);
%ages = ("Jerry", 45, "Tom", 22, "Vickie", 38);

#PRINT MY HASHES TO THE BROWSER
print %coins;
print "<br />";
print %ages;

Display:

Dime10Nickle5Quarter25
Jerry45Vickie38Tom22

Hashes are very complex data types, for now just understand the syntax of how to define one. Later we will take a closer look at these complex variables.

Posted in: PERL