Perl UNLESS...ELSE Statement

Perl Conditional Statements

An unless statement can be followed by an optional else statement, which executes when the boolean expression is true.

Syntax

The syntax is as follows:

unless(boolean_expression){
   # Executed when the boolean expression boolean_expression is false
}else{
   # Executed when the boolean expression boolean_expression is true
}

If the boolean expression boolean_expression is false, the code inside the unless block is executed. If the boolean expression is true, the code inside the else block is executed.

Flowchart

Example

#!/usr/bin/perl

$a = 100;
# Using unless statement to check the boolean expression
unless( $a == 20 ){
    # Executed when the boolean expression is false
    printf "The given condition is false\n";
}else{ 
    # Executed when the boolean expression is true
    printf "The given condition is true\n";
}
print "The value of a is : $a\n";

$a = "";
# Using unless statement to check the boolean expression
unless( $a ){
    # Executed when the boolean expression is false
    printf "The given condition for a is false\n";
}else{
   # Executed when the boolean expression is true
    printf "The given condition for a is true\n";
}
print "The value of a is : $a\n";

Executing the above program will output:

The given condition is false
The value of a is : 100
The given condition for a is false
The value of a is :

Perl Conditional Statements