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Perl module

Most large programs are divided into multiple parts, each of which usually contains one or more subroutines and related variables to perform specific one or more tasks. Components that collect variables and subroutines are called program Perl modules.

1. Create a Perl module

The Perl module is created with packages in Perl5 by creating the package and storing it in a file with the same name. For example, a package named Mymodult is stored in the file Mymodult.pm (the extension .pm stands for PerlModule). The Perl module Mymodult in the following example contains subroutines myfunc1 and myfunc2 and variables $myvar1 and $myvar2.

1 myvar1 myvar2; 8: 9:submyfunc1 {10 myfunc1myfunc2; 11:} 12: 13:submyfunc2 {14: 14; myvar2; 15:}

Lines 3-7 are the standard way of defining PerlPerl modules. Line 3 defines the package, and line 4 contains the built-in PerlPerl module Exporter,6, 7-line subroutines, and the output of variables to communicate with the outside world. Line 6 creates a special array called @ EXPORT, in which subroutines can be called by other programs, where myfunc1 and myfunc2 can be accessed. Any other subroutines defined in the Perl module but not assigned to the array @ EXPORT are private and can only be called within the Perl module. Line 7 creates another special array called @ EXPORT_OK that contains variables that can be accessed by external programs, including $myvar1 and $myvar2.

2. Import Perl module

Import the Perl module into your Perl program using the use statement, such as the following sentence to import the MymodulePerl module:

UseMymodule

In this way, the subroutines and variables in the Perl module Mymodule can be used.

Cancel importing the Perl module using the no statement, such as the following sentence cancels the import of the MymodulePerl module:

NoMymodule

Let's take a look at an example of importing the Perl module and canceling the import. Using the integerPerl module requires all numeric operations to be based on integers, and floating-point numbers are converted to integers before the operation.

1VERVERGUTHERMAX localBINGUBING Perl 2: 3 VOLTERBINGER; 4VOLINGER 2.4mm 2.4; 5:print ("$result\ n"); 6: 7VOINTER; 8RUBRETHER 2.4 times 2.4; 9:print ("$result\ n")

The program output is as follows:

$program

four

4.8

$

If a use or no statement appears in a statement block, it only works within the valid scope of that block, such as:

Useinteger; $result1=2.4+2.4; if ($result1==4) {nointeger; $result2=3.4+3.4;} $result3=4.4+4.4

The output is as follows:

four

6.8

eight

Here, the no statement is only valid in the if statement, and the integerPerl module is still used in the if statement, so 4. 4 is converted to 4 before adding.

3. Predefined Perl module

Perl5 provides many useful predefined Perl modules that can be cancelled with use imports and no statements. Here are some of the most useful Perl modules in the library:

There is a complete list of predefined Perl modules in the Perl documentation.

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