I hope I'm not breaking any rules, but this process originally started in another thread: Macro to use “λ” character as “lambda” in R5RS Scheme? But after seeing it execute properly in Racket AND Gambit I know the problem lies not in the code but in the calling mechanism, which is why I am starting this new thread. https://gist.githubusercontent.com/GlassGhost/bdf2b28f6c3592f3933a/raw/deriv... This file executes great, with the Racket shebang the file can be ran thus: ./derive.ss If I uncomment line 3 and delete lines 1-2 to change from Racket to Gambit, When I execute ./derive.ss It throws "*** ERROR IN "derive.ss"@8.33 -- Ill-formed expression". However Gambit works as great as it did earlier with Racket IF I do: scheme-r5rs -:s ./derive.ss So, how I can set "standard Scheme mode" just like the command line option "-:s" from within a Shebang Executed scheme file in Gambit??