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#! /usr/bin/perl -l
use strict;
use warnings;

sub amok {
    print "\@_ before amok: @_";

    # kill'em all by implicit alias
    for my $k ( 0 .. $#_ ) {
        $_[$k] = 'kill';
    }    

    print "\@_ after amok: @_";
}


my @wp = qw( Vater Mutter Kind );

print "start: @wp";

amok(@wp);

print "ende: @wp";

Quote

... Any arguments passed in show up in the array @_. Therefore, if you called a function with two arguments, those would be stored in $_[0] and $_[1].
The array @_ is a local array, but its elements are aliases for the actual scalar parameters. In particular, if an element $_[0] is updated, the corresponding
argument is updated (or an error occurs if it is not updatable). If an argument is an array or hash element which did not exist when the function was called,
that element is created only when (and if) it is modified or a reference to it is taken. (Some earlier versions of Perl created the element whether or not
the element was assigned to.) Assigning to the whole array @_ removes that aliasing, and does not update any arguments. ...