#! /usr/bin/perl -wl

my @proteins = qw(DAAAAATTLTTTAMTTTTTTCKMMFRPPPPPGGGGGGGGGGGG ALTAMCMNVWEITYHKGSDVNRRASFAQPPPQPPPPLLAIKPASDASD);

my %seen = map {$_ => 1} @proteins;
 
print "Peptide $_" for grep !$seen{$_}++,
        map {split /[KR]\K(?!P)/} @proteins;