use strict;
use warnings;
use Data::Dumper;

my @proteins=qw(
DAAAAATTLTTTAMTTTTTTCKMMFRPPPPPGGGGGGGGGGGG 
ALTAMCMNVWEITYHKGSDVNRRASFAQPPPQPPPPLLAIKPASDASD
);
print Dumper \@proteins;
my @new_peptides;

for my $protein (@proteins) {
	if ($protein =~ m/[K(?!P)|R(?!P)]/g) {		
		$protein =~ s/K(?!P)|R(?!P)/=/g;
		push @new_peptides, split ('=',$protein);		
	}
}
print Dumper \@new_peptides;
for (@new_peptides) {
	print "The peptide is $_\n";
}