system "clear";
print "Palindrome - gamma version\n";
print "--------------------------\n\n";
print "Please enter DNA filename: ";
$filename=<STDIN>;
chomp $filename;
	unless (-e $filename) {
		print "No such file...exiting\n\n";
		exit;
	}
	unless (open(DNASEQ, $filename)) {
		print "Cannot open file...exiting\n\n";
		exit;
	}	
@dna=<DNASEQ>;
$dna=join('', @dna);
$dna=~ s/\s//g;
$count_of_2=0;
	for ($lb=0; $lb<length $dna; ++$lb) {
			$lba=substr ($dna, $lb, 1);
			$rba=substr ($dna, $lb+1, 1);
			$rba=~ tr/atgc/tacg/;
				if ($lba eq $rba) {
					++$count_of_2;
				}
				else {
				}
	}
print "Number of 2bp palindromes: ", $count_of_2, "\n";
exit;

##</code><code>##

CGACAGCTACGATCGTAC
CAGTATCATCACTACGTA
CACGAGAGTACGATCGAC
......etc.........

##</code><code>##

$dna=~ tr/ATGC/atgc/;