Switch statement in perl

Many programming languages offer the switch/case statement but the perl programming language does not have any default switch statement built into it. Some of the newer versions of perl however have a construct named given-when which somewhat resembles the switch statement. This is not available while coding by default & has to be enabled by via the 'use feature' statement.

The syntax for using given-when is that a given value is matched against a set of values & when a match is found the corresponding block of code gets executed. There is also a default statement which is executed in case no match is found.

given (value) {
          when (value1) { some code ; }
          when (value2) { some code ; }
          default { default result  ; }
        }

This article is describes in brief the usage of given-when construct in perl via a simple script.
Given below is the script:

[root@alive ~]# cat switch.pl
#!/usr/bin/perl -w
#

use warnings;

$|=1;
use feature qw(switch);

print "system running perl version $^V \n";

##testing switch statement##
#
my $x = 10 ;
my $y = 20 ;


print "enter value: " ;
my $z = <STDIN> ;

given($z) {
        when($x) { print "you entered the nmber $x \n" ; }
        when($y) { print "you entered the nmber $y \n" ; }
        default { print "default \n" ; }
        }

This is a simple script which first prints the version of perl running on the system. It then prompts the user to enter a value. The input is then matched against the when clauses & the corresponding code block is executed when a match is found & the default statement is executed in case no match is found. 

Note: As mentioned earlier the given-when construct is not enabled by default. To enable it I've used the statement use feature qw(switch)

Here's what happens when we execute the script.

[root@alive ~]# ./switch.pl

system running perl version v5.16.3

enter value: 10

you entered the nmber 10

[root@alive ~]# ./switch.pl

system running perl version v5.16.3

enter value: 20

you entered the nmber 20

[root@alive ~]# ./switch.pl

system running perl version v5.16.3

enter value: 30

default

[root@alive ~]#