#!/usr/bin/perl

use strict;
use warnings;
use Safe;

my $safe = new Safe;
$safe->reval(q|
sub fibonacci {
        my $index = shift;
        return 0 if $index == 0;
        return 1 if $index == 1;
        return fibonacci( $index - 1 ) + fibonacci( $index - 2 );
}
|);
print "F($ARGV[0]) is ", $safe->reval(qq|fibonacci($ARGV[0])|), "\n";