use Tie::FlipFlop;
tie my $flipflop => Tie::FlipFlop => ( 'white', 'black' );

print qq|$flipflop\n|;
print qq|$flipflop\n|;
print qq|$flipflop\n|;
print qq|$flipflop\n|;

##</code><code>##

black
black
black
black

##</code><code>##

use Tie::FlipFlop;
tie my $flipflop => Tie::FlipFlop => ( 'white', 'black' );

print $flipflop, qq|\n|;
print $flipflop, qq|\n|;
print $flipflop, qq|\n|;
print $flipflop, qq|\n|;

##</code><code>##

white
black
white
black