#open data file
if (open(DNAInputFile, 'DNA_seq.txt')) {
	print "File DNA_seq.txt opened OK \n";
}
else {
	print "Cannot open file DNA_seq.txt\n";
	exit;
}

#read from file, store as array  @ for array variable
@DNA_array = <DNAInputFile>;
close DNAInputFile;  #close the input file
$RNA = join('',@DNA_array);   #convert array of chars to string

print "Here is the starting DNA sequence: \n".$RNA,"\n";  
$RNA =~ s/T/U/g;   

print "Here is the result of transcribing the DNA to RNA: \n";
print "$RNA\n";

$x = $RNA;
print "Here are the codons (3 bases each)\n";
for ($i=0; $i< length $x; $i=$i+3) {
	$subSeq = substr($x, $i, 3);
	print "$subSeq\n";
}

exit;