Except that you're not aliasing anything ;) You're making a copy of $_[0]. If you modify $self, the variable aliased by $_[0] will not be modified.

local $\="\n";

my $roy = 4;

print $roy;
print asdf($roy);
print $roy;

sub asdf {
   my $self = $_[0];
   $_[0] = 66;
   $self = 0;
   return "yoda";
}
__END__
4
yoda
66
[download]

Isn't perl fun ;)