my %turn= (
    0=>{Next=>5,Prev=>53},
    5=>{Turn=>"turn 0",Prev=>0,Next=>28},
    28=>{Turn=>"turn 28",Prev=>5,Next=>53},
    53=>{Turn=>"turn 53",Prev=>28,Next=>0},
);
sub pushTurn {
    my( $num, $turn )= @_;
    my $last= $turn{0}{Prev};
    $turn{$num}= {Turn=>$turn,Prev=>$last,Next=>0};
    $turn{0}{Prev}= $num;
    $turn{$last}{Next}= $num;
}
sub deleTurn {
    my( $num )= @_;
    my( $prev, $next )= @{ $turn{$num} }{qw( Prev Next )};
    $turn{$prev}{Next}= $next;
    $turn{$next}{Prev}= $prev;
    delete $turn{$num};
}