Conditional Statements in PERL

Conditional statements help in decision making. If a condition is true, this block is executed otherwise the program control moves to the next instruction followed by the block.

In this language, numeric value 0 , string '0' or "" , a list having no elements () , and undef represent false in a boolean context. Negation of a true value by ! or not returns a special false value.

In this context, the conditional statements are discussed below.

if statement

A boolean expression is enclosed in if , based on the condition either of the the blocks is executed as shown below.

$x = 20; $y = 10; if ($x > y) { print "x is greater than y.\n"; }

if...else statement

An if statement can be followed by an optional else statement.

$x = 20; $y = 10; if ($x > y) { print "x is greater than y.\n"; } else { print "y is greater than or equals with x.\n"; }

if...elsif...else statement

An if statement can be followed by an elsif statement, the elsif represents else if .

$x = 20; $y = 10; if ($x > y) { print "x is greater than y.\n"; } elseif (x < y){ print "y is greater than x.\n"; } else { print "x is equals with y.\n"; }

unless statement

An unless statement consists of a boolean expression followed by one or more statements.

$x = 10; unless($x <= 0){ print("x is greater than 0\n") }

unless...else statement

An unless statement can be followed by an optional else statement.

$x = 10; unless ($x >= 5){ print("x is less than 5\n") } else { print("x is greater than or equal 5\n"); }

unless...elsif..else statement

Similar to if...elsif...else , an unless statement can also be followed by an elsif statement, which in turn is followed by an optional else statement.

$x = 1; unless($x > 5){ print("x is less than 5\n"); }elsif($x == 5){ print("x is 5\n"); }else{ print("x is greater than 5\n"); }

switch statement

In latest versions of Perl, switch statement can be used to compare value of a variable against various conditions.

my $color; my $code; print("Please enter a RGB color to get its code:\n"); $color = <STDIN>; chomp($color); $color = uc($color); given($color){ when ('RED') { $code = '#FF0000'; } when ('GREEN') { $code = '#00FF00'; } when ('BLUE') { $code = '#0000FF'; } default{ $code = ''; } } if($code ne ''){ print("code of $color is $code \n"); } else{ print("$color is not RGB color\n"); }

The ? : Operator

Let's check the conditional operator ? : which can be used to replace if...else statement. It has the general form Exp1 ? Exp2 : Exp3; where Exp1, Exp2, and Exp3 are expressions. Notice the use and placement of the colon.

#!/usr/local/bin/perl $age = 10; $status = ($age > 60 )? "Senior citizen" : "Not senior citizen"; print "$status\n";

Happy Exploring!