Re: cleaving a sequence with specific alphabets

[mwah]

Its not entirely clear for me what you try to do.

...
my @s = split /
               (?<=[KR])  # split on K,R
               (?!P)      # but not if in front of a P
              /x, 'APADPKGSTIDRPDAARTLTVHKCEQTDTRGVKEGTRNEDPQAECKPVSDV
+EFTITKLNVD';

print join "\n", @s;
...

The above would be my first guess here.

Regards

mwa

[tachyon-II]

Probably not as good as the split solution but perhaps a little easier to read if you recognise the idiom:

@arr = $string =~ m/(.*?[KR])(?!P)/gs;

[mwah]

You won't need capturing parentheses when evaluating in list context. Afaik does the .*? invoke a speed penalty, so that the expression might be optimized as:

     ...
     my @arr = $string =~ /
                      [^KR]+  # collect non K|R
                      .       # the following must be K|R
                      (?!P)   # ignore if fragment would start by P
                     /gsx;                
     ...

Regards

mwa

[tachyon-II]

This is broken, not optimised. The .*? was there for a reason.

$string = "RYOURPOSTBROKEN";