Read the friendly manual more thoroughly:

perlsyn: "The experimental "given" statement is *not automatically enabled*; see "Switch Statements" below for how to do so, and the attendant caveats."

Rough digest of the referenced matter: From 5.10.1 on one can say use feature "switch"; and from 5.14 onward, you can enable switch (given/when) by specifying the Perl version.

When done per the doc, execution (under 5.16/32bit Win7) is as follows:

C:\>perl 1078449.pl
2 is Two
C:\>
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using your code with addition of line 3, specifying a version = or > 5.14:

use strict;
use warnings;
use 5.016;

sub test2 {
    my $var = 2;
    my $i;
    given ($var){
        when(1) { $i = "One"; }
        when(2) { $i = "Two"; }
        when(3) { $i = "Three"; }
        default { $i = "Other"; }
    }    
    print "$var is $i";
}

test2();
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