my @res;
my $i = 0;
while( $i < $#id ) {
    ++$i until defined $id[ $i ];
    my $id = $id[ $i ];
    my $start = $i;
    ++$i while defined( $id[ $i ] ) and $id[ $i ] == $id;
    my $end = $i - 1;
    push @res, [ int2dhm( $start ), int2dhm( $end ), $tally[ $start ] ];
}