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Perl | Boolean Values

  • Difficulty Level : Medium
  • Last Updated : 15 Feb, 2019

In most of the programming language True and False are considered as the boolean values. But Perl does not provide the type boolean for True and False. In general, a programmer can use the term “boolean” when a function returns either True or False. Like conditional statements(if, while etc.) will return either true or false for the scalar values.

Example:




# Perl Code to demonstrate the boolean values
  
# variable assigned value 0
$k = 0;
  
# checking whether k is true or false
if ($k)
{
    print "k is True\n";
}
else
{
    print "k is False\n";
  
# variable assigned value 2
$m = 2;
  
# checking whether m is true or false
if ($m)
{
    print "m is True\n";
}
else
{
    print "m is False\n";

Output:

k is False
m is True

True Values: Any non-zero number i.e. except zero are True values in the Perl language. String constants like ‘true’, ‘false’, ‘ ‘(string having space as the character), ’00’(2 or more 0 characters) and “0\n”(a zero followed by a newline charatcer in string) etc. also consider true values in Perl.

  • Example:




    # Perl Code to demonstrate the True values
      
    # variable assigned value 5
    $a = 5;
      
    # checking whether a is true or false
    if ($a)
    {
        print "a is True\n";
    }
    else
    {
        print "a is False\n";
      
    # string variable assigned white 
    # space character
    $b = ' ';
      
    # checking whether b is true or false
    if ($b)
    {
        print "b is True\n";
    }
    else
    {
        print "b is False\n";
      
    # string variable assigned 'false'
    # value to it
    $c = 'false';
      
    # checking whether c is true or false
    if ($c)
    {
        print "c is True\n";
    }
    else
    {
        print "c is False\n";
      
    # string variable assigned "0\n"
    # value to it
    $d = "0\n";
      
    # checking whether d is true or false
    if ($d)
    {
        print "d is True\n";
    }
    else
    {
        print "d is False\n";

    Output:



    a is True
    b is True
    c is True
    d is True
    

False Values: Empty string or string contains single digit 0 or undef value and zero are considered as the false values in perl.

  • Example:




    # Perl Code to demonstrate the False values
      
    # variable assigned value 0
    $a = 0;
      
    # checking whether a is true or false
    if ($a)
    {
        print "a is True\n";
    }
    else
    {
        print "a is False\n";
      
    # string variable assigned empty string
    $b = '';
      
    # checking whether b is true or false
    if ($b)
    {
        print "b is True\n";
    }
    else
    {
        print "b is False\n";
      
    # string variable assigned undef
    $c = undef;
      
    # checking whether c is true or false
    if ($c)
    {
        print "c is True\n";
    }
    else
    {
        print "c is False\n";
      
    # string variable assigned ""
    # value to it
    $d = "";
      
    # checking whether d is true or false
    if ($d)
    {
        print "d is True\n";
    }
    else
    {
        print "d is False\n";

    Output:

    a is False
    b is False
    c is False
    d is False
    

Note: For the conditional check where the user has to compare two different variables, if they are not equal it returns False otherwise True.

  • Example:




    # Perl Program demonstrate the conditional check
      
    # variable initialized with string
    $x = "GFG";
      
    # using if statement
    if ($x eq "GFG")
    {
        print "Return True\n";
    }
    else
    {
        print "Return False\n";
    }

    Output:

    Return True
    



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