Write a module that generates a frequency count of the letters in a string (number of A’s, B’s, C’s, and so on). The function should return a 256-element array whose index is the character number and whose elements are the number of times that character appears in the string.

Write a module that computes a frequency count of the pairs of letters in a string. Because returning a 256×256 element array is difficult in Perl, you’ll have to create some access functions so that the application can query the counts after you compute them.

3. Create a module to extract any number of bits from a scalar starting at any offset. For example, the function may be asked to return 5 bits in the string starting at bit index 27.

Write a module that gives a Perl program direct access to the I/O operations (in and out on the PC class machines).

Create a module that allows reading and writing of random bytes in a file. In other words, you can tell this module, “change byte 56 of the file to the letter ‘Q’.”