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if-elsif-else Statement

Explore how to implement Perl conditional statements using if, elsif, and else constructs. Learn to evaluate multiple conditions and control the execution flow based on different scenarios.

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The elsif statement

When there are different possible actions against a set of different conditions, then elsif is used to extend the if statement. The conditional block starts with an if-statement followed by multiple elsif statements, each with a different condition, and may end with an optional else-statement.

Syntax

The syntax and usage of the if-statement with the elsif statement are presented in the following example.

Perl
$score=50; #change the value of score to see other results
if ($score > 100){ # If score is greater than 100
print "Error: the score is greater than 100!\n";
}
elsif ($score < 0){ # Else If score is less than 0
print "Error: the score is less than 0!\n";
}
elsif ($score >= 50){ # Else if score is greater or equal to 50
print "Pass!\n";
}
else{ # If none above, then score must be between 0 and 49
print "Fail!\n";
}

Explanation

  • All the statements in the code above will run in order from top to bottom until a condition has been met.

  • On line 3, we check if score is greater than 100.

  • On line 6, we check if score is less than 0.

  • On line 9, we check if score is greater than or equal to 50.

  • On line 12, the else condition will execute if all the conditions above evaluate to “false”.

Changing score values

  • If you change the score to “110” the output displayed would be “Error: the score is greater than 100!”

  • If you change the score to “-20” the output displayed would be “Error: the score is less than 0!”

  • If you change the score to “48” the output displayed would be: “Fail”

Logical operators in if condition

Logical operators can possibly be used to include multiple conditions in one if or elsif statement, as given in the following example:

Perl
$score=70; #change the value of score to see other results
if ($score <= 100 && $score >= 50 ){ # If score is greater than 100
print "Pass!\n";
}
elsif ($score >= 0 && $score < 50) {
print "Fail!"
}
else{ # If none above, then score must be less than 0 or greater than 100
print "Invalid!\n";
}