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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