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    Conditional Statements in PERL

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    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.

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

    if...else statement

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


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    $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";
    }
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

    if...elsif...else statement

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


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    $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";
    }
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

    unless statement

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


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

    unless...else statement

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


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

    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.


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    $x = 1;
    unless($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");
    }
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

    switch statement

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


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    my $color;
    my $code;
    print("Please enter a RGB color to get its code:\n");
    $color = <STDIN>;
    chomp($color);
    $color = uc($color);
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

    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.


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




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