Different outputs on a program??? Is it possible?

[Alexandre Weffort Thenorio]

I've made a program that just writes a text file. So the user runs the
program and it does its job. What I want to do is that when the user runs
the program with a flag (Lets say -h) it just shows a text file on the
screen with the program explanation (Or better say help file) but otherwise
if no flag given the program does it job. The problem is that writing the
file on haskell is IO[] (I think) and outputting a text is IO[String] and
then haskell doesn't allow me to have a function where it checks if there is
flag, creating a text file if not or outputting a String if so because they
are different types of output.

Can anybody help me here??

Best Regards

Alex