/usr/lib/s9fes/help/cond-expand is in scheme9 2010.11.13-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 | S9 LIB  (cond-expand (symbol expression ...))  ==>  object
This is a subset of SRFI-0 COND-EXPAND. Each argument of COND-EXPAND
is a clause consisting of a leading "feature ID" (a symbol) and any
number of trailing expressions (a body). It evaluates to the body of
the first clause having a feature ID of SCHEME-9-FROM-EMPTY-SPACE,
S9FES, or ELSE. The body is then evaluated by S9fES. When none
of the above feature IDs is found, an error is reported.
(cond-expand (s9fes (cons 1 2)))               ==>  (1 . 2)
(cond-expand (foo (cons 1 2)) (else (+ 1 2)))  ==>  3
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