My code has a bug. The update on the $cur pointer should be:

$cur = $r->[1] unless $cur > $r->[1];
[download]

ie we only want to update it if it is greater than our last known greatest end or range. It will fail on

@array = (
    [ '00:00', '24:00' ],
    [ '01:00', '02:00' ]
);
[download]

for example.