珀尔 | wantarray()函数

Perl 中的 wantarray()函数如果当前正在执行的子例程希望返回一个列表值，则返回 True，如果它正在寻找一个标量值，则返回 false。

Syntax: wantarray()

Returns: true for list value and false for scalar values

示例 1：

#!/usr/bin/perl -w
  
# Subroutine to call wantarray() function
sub geeks
{
    return(wantarray() ? ("Geeks", "For", "Geeks") : 1);
}
  
# Calling the subroutine 
# in scalar and array context
$value = geeks();
@value = geeks();
  
# Printing the values in both contexts
print("Value in Scalar context: $value\n");
print("Value in List Context: @value");

输出：

Value in Scalar context: 1
Value in List Context: Geeks For Geeks

示例 2：

#!/usr/bin/perl -w
  
# Subroutine to call wantarray() function
sub geeks
{
    if(wantarray())
    {
        # Addition of two numbers when 
        # wantarray() function is called
        # in list context
        $c = $a + $b; 
    }
    else
    {
        # When wantarray() is called 
        # in Scalar context
        return 1;
    }
}
  
# Driver Code
$a = 10; $b = 20; $c = 0;
  
# Calling Subroutine in scalar and list contexts
$value = geeks($a, $b);
@value = geeks($a, $b);
  
# Printing values in both the contexts
print("Value when called in Scalar context: $value\n");
print("Value when called in List Context: @value");

输出：

Value when called in Scalar context: 1
Value when called in List Context: 30