my $str1 = 'ATTTA';
my $str2 =  'TTTAA';

$merged_result12 = 'ATTTAA';

##</code><code>##

my $str2 = 'ATGTA';
my $str3 = 'ATGTA';

$merged_result23 = 'ATGTA';

##</code><code>##

When there are more than one possibilities of merging
like below. We take the "last" merge.

my $str3 = 'ATGATG';
my $str4    = 'ATGATG';

$merged_result34 = 'ATGATGATG';