You can use Tie::FlipFlop for the same purpose. Here's the synopsis from the perldoc document:

 use Tie::FlipFlop;

 tie my $flipflop => Tie::FlipFlop => qw /Red Green/;

 print  $flipflop;      # Prints 'Red'.
 print  $flipflop;      # Prints 'Green'.
 print  $flipflop;      # Prints 'Red'.
[download]

It's probably too much for such a simple function but frees you from keeping the $flip variable around.

You can use Tie::Counter in the same fashion to rotate through more than two elements.