First, please always "use strict" and "use warnings". This will catch a lot of code problems, as you'll see with the example below and your "$i" declaration. Secondly, you try to call your test_func as a sub...without declaring it as a sub. Your code should look like this(you need to fix $i):

#!/usr/bin/perl

use strict; # always do this!
use warnings; # always do this!

use Switch;

my $i; # we declare it, but never assign it.
chomp(my $var = <STDIN>);

switch ($var) {
    case(1) {
        test_func()
    }
}

print "case: $i\n";  # perl complains..$i is not assigned

sub test_func {
    print "\nhello";
}
[download]