Perl switch statement

Author：Eve Cole Update Time：2024-12-24 17:12:01

A switch statement allows testing of a variable equal to multiple values. Each value is called a case, and the variable being tested is checked for each switch case .

The switch case execution is based on the Switch module, which is not installed by default.

Install the Switch.pm module

Install using CPAN

Open a command window, enter the cpan command, and then enter the install Switch command:

 # cpancpan[1]> install Switch // Install cpan[2]> exit // Exit

Ubuntu installation using apt-get

 sudo apt-get install libswitch-perl

grammar

The syntax format is as follows:

grammar

use Switch ; switch ( argument ) { case 1 { print " Number 1 " } case " a " { print " string a " } case [ 1..10,42 ] { print " The numbers are in the list " } case ( @array ) { print " Numbers in array " } case / w+ / { print " regular matching pattern " } case qr /w+/ { p r int " regular matching pattern " } case ( %hash ) { print " hash " } case ( & sub ) { print " child process " } else { print " Does not match previous condition " } }

The following are the rules for switch statements:

Scalar parameters of any type can be used in the parentheses of a switch statement.

There can be any number of case statements in a switch. Each case is followed by a value to be compared and a colon.

The scalar after the case statement will be compared with the scalar in the switch statement to determine whether they are equal.

When the variable being tested is equal to the constant in the case, the statements following the case will be executed until the break statement is encountered.

The switch statement can have an optional else statement at the end, which is executed if all cases do not match.

When the case is matched, the case statement block code will be executed, and the switch statement will jump out after execution.

After matching the case, if we need to continue executing the next case statement, we need to add a next statement.

flow chart

Example

#!/usr/bin/perl use Switch ; $var = 10 ; @array = ( 10 , 20 , 30 ) ; %hash = ( ' key1 ' => 10 , ' key2 ' => 20 ) ; switch ( $var ) { case 10 { print " Number 10 n " } case " a " { print " string a " } case [ 1..10,42 ] { print " The numbers are in the list " } case ( @array ) { print " Numbers in array " } case ( %hash ) { print " in the hash " } else { print " No matching condition " } }

Executing the above program, the output result is:

 Number 10

Next let's look at an example of using next :

Example

#!/usr/bin/perl use Switch ; $var = 10 ; @array = ( 10 , 20 , 30 ) ; %hash = ( ' key1 ' => 10 , ' key2 ' => 20 ) ; switch ( $var ) { case 10 { print " Number 10 n " ; next ; } # Continue execution after matching case " a " { print " string a " } case [ 1..10,42 ] { print " The numbers are in the list " } case ( @array ) { print " Numbers in array " } case ( %hash ) { print " in the hash " } else { print " No matching criteria " } }

Executing the above program, the output result is:

 Number 10 Numbers in the list