The install guide (http://arclanguage.org/install) is out of date. For one, the latest Arc (which works with the latest versions of mzscheme) is 3.1, which you can get from http://ycombinator.com/arc/arc3.1.tar. Secondly, mzscheme -m used to mute the "Welcome to MzScheme" banner, but now:
You might also notice that in the newer versions, ^C at the Arc prompt doesn't put you back into the Scheme REPL like it says in the install guide. If you want that option, use
(1) In the future, your post titles should be more descriptive; using more exclamation marks doesn't get you more help. :P E.g., you could've titled this post something like "Weird error. main: not defined or required into the top-level environment".
(2) To format code, put a blank line
and then but two or more spaces before the line of code
(and also for subsequent lines of code).
If it doesn't work right the first time you post, you're allowed to edit for a certain amount of time. A quick formatting reference: http://arclanguage.org/formatdoc.
