Lesson 9	Array subscripts in Perl
Objective	Access array element using a foreach loop.

Perl Array Subscripts and for loop

You can use any numeric value for an array subscript. For example, consider this array:

# AMPAS Best Picture 1980-97
@bestpix = ( 
"Ordinary People",
"Chariots of Fire", "Gandhi",
"Terms of Endearment", "Amadeus",
"Out of Africa", "Platoon",
"The Last Emperor", "Rain Man",
"Driving Miss Daisy",
"Dances with Wolves",
"The Silence of the Lambs", "Unforgiven",
"Schindler's List", "Forrest Gump",
"Braveheart", "The English Patient",
"Titanic" );

C-style for loop
Using a C-style for loop, you could print it like this:

for($i = 0; $i < scalar @bestpix; $i++) { 
 print "$bestpix[$i]\n" 
}

Perl Scalar operator in Perl

Notice the use of the scalar operator:

for($i = 0; $i < scalar @bestpix; $i++) {
 print "$bestpix[$i]\n" 
}

The value of an array in scalar context is the number of elements in the array. So the value of scalar @bestpix is the number of elements in the @bestpix array. In Perl, the type of an expression is often taken from the context, rather than a fixed set of rules. In cases where the context may be ambiguous, or give you a type that you do not expect, you can use the scalar operator to force an expression to a scalar context.

For example, this expression:

print <STDIN>;

will print all the lines from the standard input (usually the keyboard) and then finish. But what if you only want to print one line? You could use an intermediate variable like this:

$line = <STDIN>;
print $line;

Or, you could use the scalar operator to force the context to a scalar and avoid the intermediate variable altogether:

print scalar <STDIN>;

The scalar operator forces the context to be scalar, instead of the default list context for the print function call.

That method contained elements from the C programming language, and while it works fine, there are other ways to do it in Perl.

Perl foreach Loop

For example, you could use the Perl foreach loop:

foreach $pic (@bestpix){
  print "$pic\n" 
}

The results are exactly the same, yet it's a bit easier to read.
The for and foreach constructs are explained in detail later in this course.
If you are confused by the difference between a

for and a
foreach loop,

keep in mind that a foreach loop increments through a defined list of values.

A for loop has no list.
The values of a for loop are defined by a beginning value, a control condition, and an increment operator.
Here is the for loop example again:

for($i = 0; $i < scalar @bestpix; $i++)

The for loop begins with a value of $i=0, has a controlling condition of $i < scalar (when this condition is no longer true, the loop will be exited), and an increment value of $i++ or increment it one number per loop.

Perl join function

The join function joins each of the elements of a list using whatever string is specified in the first argument. Here is how you would get the same results again, using join:

print join("\n", @bestpix), "\n";

For another example, this version prints a comma-delimited list (much harder to do with the other methods):

print join(", ", @bestpix), "\n";

Access Perl Array - Exercise

These are the major methods of accessing a list or array.
Click the Exercise link below to write a program that accesses an array.
Access Perl Array - Exercise
Then, in the next lesson, we will learn about the push and pop operators, and how they work on arrays.