# program to generate the reverse complement of DNA strand

$DNA = 'ACGGGAGGACGGGAAATTACTACGGCATTAGC'; 

print "Original: ".$DNA,"\n\n";  
#seems like . and , both can join string and variable

$revcomp = reverse $DNA;   #reverse string, very powerful
print "Reversed: ", $revcomp,"\n\n";

$revcomp =~ tr/ACGT/TGCA/;   #translate A to T, C to G (1st to 2nd)
# =~ binding operator: means applying the operation on right to string on left

print "Here is the reverse complement DNA: \n";
print "$revcomp\n";

$revcomp =~ s/T/U/g;   #substitute all Ts with Us, s:substitute, g:global option
print "After T-U translation: \n";
print "$revcomp\n";

exit;