If you are actually typing mzscheme-m-fas.scm (which is not what you wrote in your original comment), that's your problem: you need to write mzscheme -m -f as.scm . (If not, I don't know what to say.)
And a stylistic note: when replying to someone, click on the link to their comment and actually reply; it makes following the discussion more smooth :)
Turns out the error was even sillier: I had to switch to the arc2 directory and then execute mzscheme -m -f as.scm. (I was not lying when I told you I was new at this). Sorry for the stylistic annoyance. Thanks for your help!
