Anonymous Monk,
CPAN is your friend. See this for your question on MD5.

You should also look at perldoc perlvar for @ARGV for command line arguments

Since there isn't a need to roll your own, it is back to CPAN for modules on command line arguments.
Click Me

As yet another reason to use CPAN - you may want to look at one of the config modules. This will allow you to have a standard config and then overide those parameters on the command line.
Links are cool

Cheers - L~R