Write a program which asks the user for a filename, then modifies that
file, replacing each tab (\t) character with 3 spaces.
Write a program which reads in lines of text and for each one
prints "Weekend!" if the line contains "Saturday" or
"Sunday", and for the other days of the week prints
"This is a workday."
Ignore capitalization in your regular expression.
Write a program which reads in lines of text and for each line does
the following: find the "words" (sequences of non-whitespace characters)
and print each one on a line by itself.