1 10/17/84  reverse_before, rvbe
 2 
 3 Syntax as a command:  rvbe STRA STRB
 4 
 5 
 6 Syntax as an active function:  [rvbe STRA STRB]
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 8 
 9 Function:  performs the same function as the before command/active
10 function, but in reverse order.
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12 
13 Notes:  The active function returns that part of STRA preceding the
14 last occurrence of STRB in STRA (before uses the first occurrence).  If
15 STRB occurs first and nowhere else in STRA, a null string is returned.
16 If STRB does not occur in STRA, STRA is returned.
17    [reverse_before STRA STRB]
18 is the same as--
19    [reverse [after [reverse STRA] [reverse STRB]]]
20 when STRB appears in STRA.  It is the same as STRA when STRB does not
21 appear in STRA.