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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