if Statement

Perl if statement allows you to control the execution of your code based on conditions. The simplest form of the if statement is as follows:

if (expression);

In this form, you can put the if statement after another statement. Let’s take a look at the following example:

my $a = 1;
print("Welcome to Perl if tutorial\n") if ($a == 1);

The message is only displayed if the expression $a == 1 evaluates to true.

How Perl defines true and false?

Both number 0 and string "0" are false.
The undefined value is false.
The empty list () is false.
The empty string "" is false.
Everything else is true.

Execute multiple statements based on a condition

if (expression) {
   statement;
   statement;
   ...
}

The curly braces {} are required even if you have a single statement to execute

if..else Statement

Perl provides the if else statement that allows you to execute a code block if the expression evaluates to true, otherwise, the code block inside the else branch will execute.

if (expression) {
   // if code block;
} else {
   // else code block;
}

Example

my $a = 1;
my $b = 2;
if ($a == $b) {
    print("a and b are equal\n");
} else {
    print("a and b are not equal\n");
}

The code block in the else branch will execute because $a and $b are not equal.

if..elsif statement

In some cases, you want to test more than one condition:

If $a and $b are equal, then do this.
If $a is greater than $b then do that.
Otherwise, do something else.

Perl provides the if elsif statement for checking multiple conditions and executing the corresponding code block:

if (expression) {
    ...
} elsif (expression2) {
    ...
} elsif (expression3) {
    ...
} else {
    ...
}