use strict;
use warnings;

while (my $line = <DATA>) {
		my @info = $line =~ /((?:^N+)?[ATGC]+(?:N+$)?)/g;
		print join(", ", @info), "\n";
}

__DATA__
NNNAAAATATGACAAAGGGGTTNNNNNNNNNNNNNNGATGTCTGGTCAATAGGAT
CGCAGCCATTAACATCTCAACAAGCCAAAAATTCCTTCTCAGAAATTCGGNNN
AAAATATGACAAAGGGGTTNNNNNNNNNNNNNNGATGTCTGGTCAATAGGAT