($x, $y, $z) = 'x'..'z';

print "Original values.\n";
show_vals();

print "This rotates them.\n";
rotate($x, $y, $z);
show_vals();

print "Why doesn't this?\n";
rotate_not($x, $y, $z);
show_vals();

sub rotate {
  @_[-1..($#_-1)] = @_;
}

sub rotate_not {
  @_ = @_[-1..($#_-1)];
}

sub show_vals {
  print "\$x: $x\n\$y: $y\n\$z: $z\n\n";
}