use Data::Dumper;

my @data = (
           ["1.6","2.2","3.4","3.6","5.4","6.2","7.1", "8.1", "9.0"],
           [    1,    2,    5,    6,    3,  15,    4,     3,     4],
           [ sort { $a <=> $b } (1, 2, 5, 6, 3, 15, 4, 3, 4) ]
         );


splice(@{$data[0]}, 1, 0, "2.1");
splice(@{$data[1]}, 1, 0, 7);
$data[2] = [sort { $a <=> $b } @{$data[1]}];

print Dumper(\@data);