珀尔 |布尔值

在大多数编程语言中，True 和 False 被视为布尔值。但是 Perl 没有为 True 和 False 提供 boolean 类型。通常，当函数返回 True 或 False 时，程序员可以使用术语“布尔值”。像条件语句（if、while 等）一样，对于标量值将返回 true 或 false。

例子：

Perl

# 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";
}

输出：

k is False
m is True

真值：在 Perl 语言中，任何非零数（即除零之外）都是真值。字符串常量，如'true' 、 'false' 、 ' ' （以空格作为字符的字符串）、 '00' （2 个或更多 0 个字符）和"0\n" （字符中的零后跟字符串）等. 还要考虑 Perl 中的真值。

• 例子：

Perl

# 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";
}

输出：

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

假值：空字符串或字符串包含单个数字 0或undef值，零被视为 perl 中的假值。

• 例子：

Perl

# 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";
}

输出：

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

注意：对于用户必须比较两个不同变量的条件检查，如果它们不相等，则返回False否则返回True 。

• 例子：

Perl

# 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";
}

输出：

Return True