Perl |参考文献
在 Perl 中，我们使用变量来访问存储在内存位置的数据(所有数据和函数都存储在内存中)。变量被赋予在各种操作中使用的数据值。 Perl Reference 是一种访问相同数据但使用不同变量的方式。Perl 中的引用是保存另一个变量位置的标量数据类型。另一个变量可以是标量、散列、数组、函数名等。嵌套数据结构可以很容易地创建，因为用户可以创建一个包含对另一个列表的引用的列表，该列表可以进一步包含对数组、标量或散列等的引用。
参考创建
您可以为标量值、散列、数组、函数等创建引用。为了创建一个引用，定义一个新的标量变量，并通过在它前面加一个反斜杠来为它指定变量的名称(您想要创建它的引用)。
示例:引用不同的数据类型:
# Array Reference
# defining array
@array = ('1', '2', '3');
# making reference of array variable
$reference_array = \@array;
# Hash Reference
# defining hash
%hash = ('1'=>'a', '2'=>'b', '3'=>'c');
# make reference of the hash variable
$reference_hash = \%hash;
# Scalar Value Reference
# defining scalar
$scalar_val = 1234;
# making reference of scalar variable
$reference_scalar = \$scalar_val;
注:
-
A reference to an anonymous hash can be created using the curly brackets {} around the key and value pairs.
示例:
```perl
creating reference to anonymous hash
$ref_to_anonymous_hash = {'GFG' => '1', 'Geeks' => '2'};
```
-
A reference to an anonymous array can be created using the square brackets [].
示例:
```perl
creating reference to an anonymous array
$ref_to_anonymous_array = [20, 30, ['G', 'F', 'G']];
```
-
A reference to an anonymous subroutine can also be created with the help of sub. Here there will be no name for the sub.
示例:
```perl
creating reference to an anonymous subroutine
$ref_to_anonymous_subroutine = sub { print "GeeksforGeeks\n"};
```
-
无法创建对输入/输出句柄的引用，即目录句柄和文件句柄。
取消引用
现在，在我们进行了引用之后，我们需要使用它来访问值。取消引用是访问引用所指向的内存中的值的方式。为了取消引用，我们根据变量的类型使用前缀 $、@、%或& (引用可以指向数组、标量或散列等)。
例 1:
*# Perl program to illustrate the
# Dereferencing of an Array
# defining an array
@array = ('1', '2', '3');
# making an reference to an array variable
$reference_array = \@array;
# Dereferencing
# printing the value stored
# at $reference_array by prefixing
# @ as it is a array reference
print @$reference_array; *
*Output:
123
```*
***例 2:***
```perl
*# Perl program to illustrate the
# Dereferencing of a Hash
# defining hash
%hash = ('1'=>'a', '2'=>'b', '3'=>'c');
# creating an reference to hash variable
$reference_hash = \%hash;
# Dereferencing
# printing the value stored
# at $reference_hash by prefixing
# % as it is a hash reference
print %$reference_hash; *
*Output:
3c2b1a
```*
***例 3:***
```perl
*# Perl program to illustrate the
# Dereferencing of a Scalar
# defining a scalar
$scalar = 1234;
# creating an reference to scalar variable
$reference_scalar = \$scalar;
# Dereferencing
# printing the value stored
# at $reference_scalar by prefixing
# $ as it is a Scalar reference
print $reference_scalar; *
*Output:
```perl 1234
```*
