use strict;
use warnings;
use List::MoreUtils qw(natatime);

my $str="AJKDHAKAESRADADKLASRRASDASDKASEKA";
my @ar = split '(?<=[KR](?!P))', $str; #to split where i ever i see a K or R.
print "ar: @ar\n";

my @new;
my $it = natatime 2, @ar;
while (my @vals = $it->()) {
    push @new, (join '', @vals);
}
print "new: @new\n";

##</code><code>##

ar: AJK DHAK AESR ADADK LASR R ASDASDK ASEK A
new: AJKDHAK AESRADADK LASRR ASDASDKASEK A