Perl - While Loop

A loop statement allows a program to execute a given block of codes repeatedly under a given condition. This enables a programmer to write programs in fewer lines of code and enhance the code readability. Perl has following types of loop to handle the looping requirements:

while loop
do-while loop
until loop
for loop

The While Loop

While loop allows a set of statements to be executed repeatedly as long as a specified condition is true. The While loop can be viewed as a repeating if statement.

Syntax

while (condition) {
  statements;
}

Flow Diagram:

In below mentioned example, program uses while loop to sum all integers from 1 to 5.

$i = 1;
$sum = 0;

while ($i < 6){
  $sum = $sum + $i;
  $i++;
}
print($sum);

The output of the above code will be:

The Do-While Loop

The Do-While loop in Perl is a variant of while loop which execute statements before checking the conditions. Therefore the Do-While loop executes statements at least once.

Syntax

do {
  statements;
}
while (condition);

Flow Diagram:

In the example below, even if the condition is not fulfilled, the do-while loop executes the statements once.

$i = 10;
$sum = 0;

do {
  $sum = $sum + $i;
  $i++;
} while ($i < 6);
print($sum);

The output of the above code will be: