There's a difference between the entry I submitted for qobi and the one that got accepted with Guile: since qobi doesn't have read-line, I had to define a read-line function using read-char. I don't see how this should be an issue, though.
Guile's read-line seems to be written in C.
Here's the read-line I used:
(define read-line
(lambda ()
(let loop ((acc '()) (c (read-char)))
(cond ((eof-object? c) (if (null? acc) c (list->string (reverse acc))))
((char=? c #\newline) (list->string (reverse acc)))
(else (loop (cons c acc) (read-char)))))))
If you're going to test it, you can use submissions 622748 (the one that was accepted with Guile) and 627282 (same code as the other one, but with the read-line defined above - TLE with qobi).
Thanks!