A first program

Outputs all input in reverse¹:
        #!/usr/local/bin/csi -s
        (use utils srfi-13)
        (display (string-reverse (read-all)))
        (newline)
¹) plus a newline character
Saved as "rev.scm", run it:
   $ echo -n hello world | ./rev.scm
   dlrow olleh
   $

Nice for exploring APIs and data structures!