my @range = ([35, 55], [50, 60], [30, 40], [60, 65], [70, 80]);

@range = sort { $a->[0] <=> $b->[0] } @range;

for (my $i = 0; $i < @range; $i++) {
    my $e = $range[$i][1];
    for(my $j = $i+1; $j < @range; $j++) {
        unless($range[$j][0] > $e) {
            $e = $range[$i][1] = $range[$j][1];
            splice @range, $j, 1;
            redo;
       }
   }
}

use Data::Dumper;
print Dumper \@range;

##</code><code>##

$VAR1 = [
          [
            30,
            65
          ],
          [
            70,
            80
          ]
        ];