use strict;
use warnings;

my $str="AJKDHAKAESRADADKLASRRASDASDKASEKA";

my @parts = $str =~ m/((?:[^KR]*[KR]){2})/g;
print "@parts\n\n";

@parts = $str =~ m/((?:[^KR]*[KR]){3})/g;
print "@parts\n";