#! /usr/bin/env perl
use strict;
use warnings;
use 5.020;


sub function {
	# arguments are aliased to @_
        # Overwrite the first argument
	$_[0] = "Hallo Welt";
}

my $foo = "Hello World";

say "Vorher: $foo";

function($foo);

say "Nachher: $foo";


__END__;