#!/usr/bin/perl

use feature 'switch';
use strict;

require "lib.pl";

my $global_variable1='a';
my $global_variable2='b';
my $global_variable3='c';

given( subroutine1() ){
     when (0) { subroutine2($global_variable1) }
     when (1) { subroutine2($global_variable2) }
     when (2) { subroutine2($global_variable3) }
}

#!/usr/bin/perl
# lib.pl

use strict;

sub subroutine1 { return rand(3); }
sub subroutine2 { print shift; }