Perl - If else

This tutorial explains how to use if-else conditional statements in Perl with examples.

if conditional statements are used to execute code blocks based on a conditional expression. Perl provides the following conditional statements

It provides the following features

• simple if statements
• if else statements
• if else if else
• nested if else

Simple Perl if conditional statement

if the conditional statement is used to execute code block based on conditional expression statements.

Syntax:

if condition_expression
    //code block

-The condition_expression contains either single or multiple conditions. Multiple conditions are used with logical operators.

condition_expression is always evaluated as true or false. if it is true, It executes a code block.

Here is an example

if(conditional_expression){
   code_statement;
   code_statement;
  code_statement;
}

• if is a keyword in Perl
• conditional expression are always enclosed () and must require for simple condition
• code statements are enclosed in {} and it is compulsory to include for single statement also

conditional_expression is a Boolean expression that returns true or false.

• if the condition is true, the code block is executed.
• if the condition is false, the code block is not executed. Here is an example of Perl if statements example for checking even numbers.

my $number=20;
if ($number%2==0) {
   print("Even Number")
}

Output:

Even Number

Here is a simple if conditional statement example for Odd numbers

my $number=21;
if ($number%2!=0) {
   print("Odd Number")
}

Output:

Odd Number

Perl if else conditional statements

if else in Perl is used to execute code statements based on true and false conditional expressions.

Syntax:

if (condition){
    //code block based on true conditional value
    }
else{
    // code block based on false conditional value
    }

condition is a Boolean expression that returns true or false

• if the condition is true, code block inside if block is executed.
• if the condition is false, the code block inside the else block is executed. Here is an example of Perl if conditional true example

Here is a Perl if else conditional expression example

my $number=11;
if ($number%2 == 0) {
   print("Even Number")
} else {
   print("Odd Number")
}

Output:

Odd Number

Perl if else if statement example

This is a combination of if-else and if statements.

This is used to execute code blocks based on multiple conditions.

Syntax:

if (condition1){
    code block executes based on the condition1 that is true
    }
elsif (condition2) {
        code block executes based on the condition2 that is true
        }
else{
    code block executes based on the condition1 is false
}

Here is an example

my $number=8181;
if ($number < 9) {
    print("Single-digit number")
}
elsif (($number > 9) && ($number<99)) {
    print("Two digit number")
}
elsif (($number > 99) && ($number<999)) {
    print("Three digit number")
}
else {
    print("Four digit number")
}

Output:

Four digit number

perl if condition with and operator

The conditional expression contains logical Operator Logic And operator( and or &&) Logic OR operator( or or ||) Logic Not operator( not)

In the above example, the Logical And operator are used in multiple conditions. It returns true if both conditions are true, else returns false.

my $number=76;
if ($number < 9) {
    print("Single-digit number")
}
elsif (($number > 9) && ($number<99)) {
    print("Two digit number")
}
elsif (($number > 99) && ($number<999)) {
    print("Three digit number")
}
else {
    print("Four digit number")
}

Perl If condition string example

We can check whether given two strings are equal or not using Perl if the conditional statement

Strings are equal or not using == and eq operator in If statements.

• == is numeric comparision operator, that evaluates both operands to numeric value(0) and compare its value.
• The eq operator is a string comparison operator that compares two string characters that are equal with the exact case.

my $str="test";
# using == operator
if ( $str == "test") {
    print("string are equal using == \n")
}

# using the eq operator
if ( $str eq "test") {
    print("string are equal using eq")
}
## using the eq operator
if ( $str eq "Test") {  # evaluates to false, both are different in case-sensitive
    print("string are equal using eq")
}

Output:

string are equal using ==
string are equal using eq

Perl one line if statement

Perl supports if-else statements in a single line using the ternary operator

For example, here is an if-else statement in Perl.

sub find_age {
    my $age = 40;
    my $result;
    if ($age >= 60) {
        $result = "Senior Citizen";
    }
    else {
        $result = "Not Senior Citizen";
    }
    return $result;
}

The same above can be rewritten using short hand ternary conditional operator

my $age=40
print ($age < 10) ? "Child" : ($age < 18) ? "Teenage" : ( $age <60> 18) ? "Man" : "Senior";