Write a Perl script that computes the complement of a DNA sequence.  In other words,
your script should convert all A's to T's, C's to G's, G's to C's, and T's to A's. Your
script should not use the search and replace operators in Perl such as s/// and tr///.

Hint: Use a for loop.

The input is one sequence in FASTA format in a file called "dna.txt".

For example if the file contains 

>human
ACCGT

then the output of the program should be TGGCA. Note that your program should work for 
any sequence in this format and not just the given example.

Submit a hardcopy in class on Sept 22nd.