Thanks so much for your respons, Mr.jdporter.
If that's the case the result will be:

my $sample6 =   |str1 str2 |index = 1
                |__________|         
                |str3 str4 |index = 5

                |str3 str4| index =  5
                |_________|
                |str5 str6| index = 6

$output_sample6 = [ $str1,
                    $str2,
                    $str3,
                    $str4,
                    $str3,
                    $str4,
                    $str5,
                    $str6,
                ];
[download]

I truly don't know how to go about it.
Thanks and hope to hear from you.